Why airlines make flights longer on purpose
bbc.com
bbc.com
Here the airlines are doing pretty much exactly what I, as a passenger, want, which is to predictably arrive at an airport by a certain time more often. If a plane takes less time to fly somewhere some of the time because of weather, timely takeoff from departure airport, landing slot availability at the arrival airport or whatever, I don't really care. If they arrive late however, that can be a huge problem, particularly for making connections.
As for CO2, the plane flying slower is more fuel-efficient. Isn't this lower CO2 emissions?
40 years ago there were so many fewer planes in the skies. You could fly as fast as you want, take off when you want (pretty much) and land when you want. Well, lack of satellite navigation and tracking mattered but basically the skies were less crowded. Just the other day I flew out of NYC and it took us 40+ minutes of being in a queue to take off behind 15-20 other planes because reasons. You have to have that padding in your schedule.
Guess what the engines are doing at this time. Even worse if they tell planes to circle before landing because there are too many landings at this time.
Usually one engine is turned off...
Note that the bottom half of the article is a sales pitch for his business flow product!
Quite often airliners arriving at my local airport ask ATC for a dogleg course for 'additional track miles' on approach to pad their arrival time or burn-off fuel.
It's purely a request by the pilots, not a traffic issue. CO2 being traded directly for convenience.
There are also maximum landing weights (which are different from max takeoff weights) which could potentially be a factor.
Possibly lower emissions per minute, but if they are in the air for significantly longer, then that may be cancelled out by the extra time.
Often, although fuel efficiency drops off sharply as you go above a certain speed in a vehicle, going slower than that speed is not significantly more efficient per minute, and can therefore be less efficient per distance.
Driving a car for 100 miles at 30MPH is typically less efficient than doing so at 60MPH. Driving that distance at 90MPH is even less efficient.
Fuel expenditure falls in to two buckets:
1. Moving the vehicle. Accelerating to cruising speed and fighting the deceleration of friction and air resistance.
2. Keeping the vehicle running. Lights, climate control, that sort of thing.
My guess would be that the vast majority of fuel usage for planes is (1) not (2). As evidence of this, airlines care deeply about costs. It's not a high margin business (any more). My argument is that if it wasn't overall more fuel efficient to fly slower airlines just wouldn't do it. More evidence, the latest planes (A350, B787) have a lower cruising speed than, say, the 747. This also wouldn't be the case (IMHO) if it didn't decrease fuel costs.
Also, is it necessarily fuel costs behind the decision to steer away from 747, or could it be other costs, like plane utility and capacity, parts and service cost, and the requirements of cross training?
If an aircraft even has the capability to hover in place, it usually has to expend even more fuel to do so than flying an orbit or holding pattern. The ideal way for an aircraft to handle the counter-gravity force is to push an infinite amount of air downward at infinitesimal speed. A helicopter would want to have infinitely long rotor blades, rotating at an imperceptibly slow rate. Obviously, we can't do that, so very long blades spinning slowly enough to see them move is the best compromise we can manage. The output of a jet engine is a relatively small amount of air, moving very fast, but the jets push the craft though the atmosphere, and the wings translate that forward motion into pushing a larger amount of air downward just a little bit, for more efficient lift. Vectoring the engine thrust downward to hover in place means you lose that efficiency boost from the wings. Also, rotary-wing aircraft that are heavily-laden experience "coning", which reduces hover efficiency by making the force from each wing slightly off vertical, and some of the lifting energy goes into canceling out a lateral wobble.
Keeping a plane in the air for another 15 minutes of fighting gravity just isn't significant compared to the effects from changing its speed away from the aircraft's efficiency optimum in order to arrive 15 minutes later, or from fighting air resistance by doing a holding pattern at optimal speed and altitude for enough extra distance to expend another 15 minutes. As long as the flaps are not extended, the plane is just not very concerned with gravity.
Also, once you hit about 11 km/s, you don't need to expend any more energy on counteracting gravity, anyway. At that point, it's all about atmospheric drag.
An approximate description of a train.
For many vehicles, the difference in that factor between running at ideal cruising speed (the 60MPH car in both of our examples) and a lower speed is minimal, and could well be offset or overtaken by the extra spend in (2). This is my 30MPH car example.
Running at a higher than ideal speed is inefficient in this factor and increases fuel usage a lot. This is your 120MPH (my 90MPH) example.
As you say, airlines care deeply about costs. It is highly unlikely that they were mostly running their planes inefficiently above design cruise speed, and are now slowing down to at or below the design cruise speed. It is more likely that they have always been at around the optimal speed, and are now going slower than that to reduce the risk of fines.
For example, the latest thing American Airlines seems to be doing is changing schedules in radical ways between time of purchase and day of travel. The last three itineraries I've had on American, I've gotten an e-mail weeks after buying the ticket saying that one of my flights now had a schedule several hours after the originally booked and ticketed flight. What then, predictability?
If this is recent however it's not entirely their fault. AA is a big customer for the 737 MAX. That plane's grounding has hit their schedule pretty hard. Most of those flights involved Miami for some reason but to backfill those routes they've taken planes off existing routes that weren't fully utilized. Like I'm fairly sure some weekend JFK-SEA flights were canceled and my guess was to free up an old 737 for some other route.
They're also the largest airline in the world I believe so i can't even begin to imagine the complexity of the logistics of this like making sure you have a flight crew in the right place as well as all the other changes to services like maintaining the plane, cleaning it after a flight, baggage handling, stocking the plane with food and drinks and so on.
If your changes in itinerary were less recent than that then my next question is does this involve regional flights? I fly between hubs mostly so I haven't had that experience.
Effectively they are operating a fleet that is 2.5% smaller than normal. I expect some impact to their schedule, but it shouldn't hit it that hard.
It's counter-intuitive, but an aircraft can be more efficient at higher airspeeds. The reason for this is that, unlike a ground vehicle, an aircraft in level flight must expend energy generating lift to balance its weight. This loss of energy shows up as lift-induced drag [1]. As airspeed increases, the losses to lift-induced drag decrease, while the losses to aerodynamic drag increase. Where the point of minimum total drag lies depends on several factors including weight and altitude. See [2], which contains a chart for a generic aircraft which is 5% less efficient at Mach 0.72 than it is at Mach 0.80.
1. https://en.wikipedia.org/wiki/Lift-induced_drag
2. http://atmseminar.org/seminarContent/seminar11/papers/481-Je...
It's like if someone said, "going a little slower on the highway [typically ~60 mph+] saves on fuel" and someone pedantically ButAkshully'd that cars are more efficient at 40 mph than 30 mph because of engine performance.
Edit: Ironically, I'm the one normally promoting my "Scylla-Charybdis heuristic", that you should be able to identify when tweaking a parameter goes too far. But here I think the context of the tweak was clear enough that this caveat was a distraction from the core point.
In practice they save fuel by flying slightly slower. But, their are many other considerations like weather that cause airlines to fly slightly outside of optimal altitudes and speeds.
As another commenter pointed out, even if the gate isn't ready yet, there's always room to wait somewhere on the taxiway (this has happened to me a few times recently). They'd rather wait on the ground with the engines idling than circling around in the air with the engines running at speed. Plus, it's not like gate availability is affected by schedule padding anyway; there's only so many gates at an airport, and they always are trying to turn over planes as fast as possible.
It used to be any two flights even remotely close to landing and departing time and I was really hesitant to book them .... less so now.
This is the industry that generated the famous story where American saved $40,000/year by going from two olives to one in their in-flight salad. United saved $300,000/year by printing their magazine on lighter paper. If you work at an airline and find a way to shave off a dime in fuel costs per flight, you’ll get articles written about you. And we’re supposed to believe that these companies don’t care about wasting fuel now that their schedules are padded out a bit?
To add to your list of examples. KLM, for instance, was one of the first to introduce a system that would allow certain flight data to be uploaded into the flight computer as opposed to be requiring the pilots to enter it by hand. Other than fewer errors, they touted potentially saving pilots a couple minutes of data entry as one of the chief gains of the system.
Article tl;dr -- Airlines used to get from airport to airport faster. Airlines used to be late a lot of the time. Airlines increased their estimated flight times in order to achieve higher on-time percentage. The reason they did this instead of just being faster is that they love using more fuel.
I'm not anywhere near the airline industry myself. The next time I see misreporting on my own company or industry I'll look back at this and remind myself it could be worse.
"The secret to become millionaire is to be a billionaire and buy an airline"
That's not the populist notion on corporations at all. The populist notion is that corporations' incentive structure, set by their board/leadership, causes them to act at the expense of rank and file workers and consumers.
That's very different than "evil" or "stupid".
They are models, specifically sanctioned by law, that are organized around particular sets of interests.
Just because there are subsets of people whose self-interest is aligned with particular corporations' doesn't mean that those interests are aligned with the self interest of everyone, or even a majority of people.
And this isn't to say that there isn't an important role for corporations to play in the world, but to suggest that their form and function is the result of everyone acting in their self interest is oversimplifying things dramatically.
This is exactly how developers need to think about how they communicate schedules to management. Missing an agreed upon date is usually a much bigger deal than pushing the agreed upon date out from the get go.
I was flying to Edinburgh for Christmas a couple of years ago, we were slated to leave at 9pm and arrive at 9am (7 hour flight + 5 hour time difference, made sense).
Then the plane was late getting to us, and they didn't arrive until 9:30, they quickly kicked out the passengers, then the new crew climbed aboard to start cleaning. By 10pm, we were still waiting in the terminal. at 10:45, we were finally allowed to board the plane, and after a couple of minutes it backed away from the gate and taxied to the runway, where we sat for over an hour. We were the last scheduled departure, and when the plane arrived late, the de-icing crew had gone home. We didn't leave until after midnight.
And we arrived... at 8:45 am, 15 minutes earlier than scheduled.
I slept, so I'm not sure if we hit some massive jet stream, or a black hole, or what, but that was the day that I stopped believing flight times.
Edit: Took this photo[1] waiting outside the hotel for an early check-in.
1: https://megapickles.photo/2017/12/25/reflections-of-edinburg...
I suppose "flight time" should technically be defined as "time in the air", but realistically, "time it will take you to get from airport A to airport B" is a much more useful metric to passengers.
When your plane is extremely delayed, to the point that you're the last flight taking off from your airport (and thus likely a large set of local airports), this makes the likelihood that a huge amount of airspace is more clear around your flight path now than it was for the originally scheduled flight. The updated flight path might be massively more efficient, hit favorable wind conditions, open up different speed options along the way, etc.
Since flight times are dependent on a large amount of conditions that are pretty volatile with respect to time, the original estimate was probably true, but with changing conditions and flexible scheduling, they managed to get you where you were going on time.
So, sure, maybe the 'flight time' isn't true, but it's a pretty clear indication the arrival time is.
The leading "What airlines don't want you to know" tone of this post is probably to manipulate the reader into reading the whole article, so you can find out what "they don't want you to know", which never really comes.
>Just the other day I flew out of NYC and it took us 40+ minutes of being in a queue to take off behind 15-20 other planes because reasons.
That anecdote is exactly why the claim that there is no incentive for airlines to increase efficiency is so bogus. The vast majority of scheduling delays occur because of on-the-ground and ATC issues that are the sole responsibility of the airports involved. An airline can't do much to combat the inefficiencies that result from a notoriously incompetent airport and their inability to properly manage traffic so gates clear on time.
It is not only about fuel. Right? Article is talking about punctuality. People will use competitors if an airline is not on-time. So with padding they create a safety gap to make sure they arrive on-time.
I believe 15mins safety gap is fair as it is extremely difficult and expensive to always operate on-time without a major airport redesign and technological advancement in how the system works. It gives passengers a reliable arrival time to plan whatever they have next.
So, padding, according to this article has a negative environmental impact. But that argument isn't justified and doesn't make sense, most time lost is either unavoidable for the airline (e.g. airport problems/weather) or at a phase of travel without the engines running (boarding delays, waiting for a gate, etc).
Flying slower is actually a environmental win since aircraft are more efficient at slower speeds (although costs more to the airline due to staffing/opportunity cost).
They seem to want us to believe that if padding was removed, and airlines magically got more efficient, that they'd use less fuel but what is the mechanism? What phase of flight sees the fuel reductions? It is like they don't know that aircraft often use either ground-power or only the generator while waiting.
In fact the core premise of the article is clickbait. Oh no, airlines are making sure you can plan your travel times accurately by accounting for common delays within a route! The horror! Sorry, but not biting today.
Do you have any more information on this? Obviously slower-speed turboprop planes are much more efficient than jet powered planes, but I've read in the past that flying a jet engine slower can actually increase fuel consumption and increase emissions.
Modern flight management systems have economy calculators that can predict not only fuel-at-destination figures, but can incorporate winds and other airline cost indices (crew, maint reserves, etc) to emit an "ECON" speed target.
It is only speeds below the MRC that cause a decrease in (still-air) fuel efficiency. Airlines do not typically operate in that speed range in cruise absent an ATC directive to slow down to avoid holding ahead. (Obviously, flying a hold is done below MRC as well.)
So slowing down under those speeds will decrease efficiency, but typically the airline's cost index (~additional hourly cost to operate, like crew cost) will typically push the speeds higher to minimize the overall cost.
http://www.eaa1000.av.org/technicl/perfspds/perfspds.htm is about the best thing I can google right now as a reference.
I feel like basically all the BBC articles I've seen posted here recently are nothing more than clickbait. Does anyone else feel the same?
It's not just written media either - I hear Radio 1 news sections from time to time in the car, and they are so basic and devoid of information it's like they're designed for young children.
Also, planes sitting on taxi lanes burning fuel with six planes in front of them is a common issue. Planes are assigned landing and take off slots and if they miss those, that's a problem.
So, if the schedule is unrealistic, planes might be taking off "on time" knowing full well they'll be circling downtown London for some time.
That's of course aside from the inevitable issues arising from operating at 99% capacity. Anyone familiar with queuing theory or logistics knows that this just means things pile up at the cost of delays and extra fuel being burnt. So, that too is poor planning. You never operate systems with queues at close to 100% capacity unless you are looking for severe cost overruns and bottlenecks.
This poor planning results from misaligned incentives. Airports can just park planes in holding patterns for however long they desire. It's not their fuel being burnt. So they over provision knowing full well they will have planes in holding patterns throughout the day, This maximizes their revenue. So they are actively incentivized to do this. Likewise, airlines buy fuel cheaply and only get penalized for being late. So they are incentivized to implement padding.
So, the fix is re-aligning the incentives for airports and airlines to minimize planes in holding patterns and fuel being burnt. There are several ways to do this but the bottom line would be making sure both airlines and airports aim to not have planes in holding patterns because that costs both of them something.
They hardly burn any fuel when they are waiting in the lane. The real consumption occurs when they get airborne.
Of course they consume more after they take off and in holding patterns. But sounds like there's some gains to be made here.
It's not a staff writer. I always check these things once I started to realise that some of the biases I saw in news reporting were actually determined actions by a relatively small number of independent writers.
Here's her bio on Forbes: https://www.forbes.com/sites/kathryncreedy/#4c0ca61271e2 (though she's an independent writer as far as I can tell).
In my experience the BBC buys up a fair amount of stuff to just "fill up" the offering. Usually it's pretty poor quality. I don't actually have an opinion on this piece since I know nothing of the subject. I just want to encourage people to understand where their "news" comes from.
Moving the goalposts. The article tries to make it look like a bad thing, like they're skirting their responsibilities (avoiding payouts), not improving their efficiency and punctuality (which is down to late passengers, which they either have to wait for or have to remove their luggage for, OR other factors outside the airlines' control), and that it's bad for the environment. But what if, and this may sound totally wild here, what if the schedules were too tight to begin with and they've just been adjusted to compensate?
I mean yes, the article makes mention that thanks to padding, a lot of flights seem to arrive early. But is that a bad thing? It means there's a lot more space to play around in. And planes can fly a bit slower, or fly at whatever speed they are most efficient at, instead of having to rush.
To be fair though, the point of the compensation is because a delayed flight is _very_ inconvenient. If they're removing that inconvenience by landing at the time they said they would so you can make your plans, then that's completely fine.
In a perfect world this would be solved by having a 90/95/99% percentile arrvial window rather than an arrival time.
Or perhaps more properly, re-setting expectations. If you can’t stick to your own schedule, give me one you can stick to. I’m of course reiterating what you already said (“adjusted to compensate”), but from a customer POV I’m going to be less upset if I’m early than if I’m late.
Low fuel prices currently allow planes to compete with trains for domestic flights in Germany even when the time gained is dubious at best. E.g. Berlin to Munich is a 50-60 minute flight and a 4 hour train journey. However, the train has no checkin and boarding queues and gets you from the downtown area of Berlin to the downtown area of Munich instead two 30-40 minute taxi rides away. If you factor that in, the train starts looking pretty damn good. Flying is still a little faster but so much less convenient.
It might also inform their choices for looking more fuel efficient alternatives. E.g. Berlin-Munich is well in range of the several electrical planes currently under development. IMHO a fleet of hundreds of these could revolutionize domestic flights by allowing cheap, clean flights directly between small city airports that are currently impossible to fly to because of noise and runway length.
Problem for this is that it needs coordination at least on a continent-spanning scale. If the UK decides to tax av fuel but any one of the Netherlands or France or Germany don't, Heathrow stops being a hub airport pretty damn quick, hurting both the economy and the flight options of southern England.
Just like with corporate taxes, countries have an incentive for a race to the bottom, so coordinated action is needed.
Sounds like a job for EU and/or the US federal government.
1. They would load up with maximum fuel for inbound flights. Carrying all this extra fuel means they need to burn a bit more fuel for the inbound flight.
2. They would skimp on fuel for outbound flights. This produces a risk of a low-fuel emergency.
3. Many outbound flights would stop just outside the EU for fuel. The additional stop would burn more fuel. Norway, Iceland, Russia, Switzerland, Serbia, Ukraine, and Turkey would all become busy refueling stops.
I think most of us can appreciate the logistical challenges keeping increasingly busy airports running on time, and whilst we need to ensure operational improvements are being made I don't think airlines are deliberately ignoring this (in an age of squeezed profits, being more efficient is the only way to go for them). Padding just makes sense.
The whole article has the petulant tone of someone having a hissy fit over not getting everything he would like.
As for carbon emissions, I'm guessing that whatever padded on time is spent at the gate isn't really an issue, it's more about drawn out approaches when landing. It seems perfectly reasonable to me that something like this happens when you have so many planes entering and leaving an airport, it's amazing to me that things go as smoothly as they do. Plane travel isn't going anywhere and it seems a little absurd to me that flight time needs to be completely min-maxed down to the minute due to carbon emissions, there are definitely easier and more effective ways to control this.
> It’s called “schedule creep”, or padding. And it’s a secret the airlines don’t want you to know about, especially given the spillover effects for the environment.
So… let me get this right… because the announced scheduled arrival time is announced as being an hour later than usual… somehow the plane spends more time in the air and is worse for the environment…
I think the author missed their morning cup of coffee.
> Padding drives higher costs in fuel burn, noise and CO2
Again, with the unsubstantiated and ludicrous claim that an airline giving itself room on the schedule for operational issues not to cause cascading effects somehow means more time in the air, more noise, and more emissions.
I give up. I hope nobody takes this article seriously.
I suspect the net effect is actually a decrease in CO2 emission because the delay stack at the end of the day doesn't force pilots to bump the throttles a little to cut some time on flights with lots of connections as I've seen them do before.
I really feel this is a matter of organizational skill and planning. The US airlines just do not care to put in the effort.
Solution: "Why don't we give more accurate arrival times, so passengers can be more confident in those stated arrival times and minimize disruption to their travel plans"
The Guardian: "This is bad for the environment"
Literally the article is saying that when airlines stopped optimistically lying about arrival time, this somehow poisoned the planet. Despite the fact that both before and after the change being complained about, flights took off at the same real timestamp, spent the same amount of real time in the air, and landed at the same real timestamp.
On the other hand, if it's an article about how "PMs ruin software engineering by pushing for unrealistic deadlines", all of a sudden a job role that depends largely on just people and their (fairly reliable) computers justifies 2x or 3x the time estimates.
The return trip was different, if the plane had departed on time it would have reached London at a time when inbound flights are not allowed due to noise restrictions. That meant it was about 2am by the time I was able to board the plane, again not ideal for sleeping.
First, to suggest that padding comes at the expense of operational improvement is wrong; well-applied padding is operational improvement.
Second, some of those time losses are due to the move from turbojets (which are fast, screamingly loud, and inefficient) to high-bypass turbofans (which are slower, quieter, and much more fuel efficient).
More time is lost as planes usually have to fly complex noise-abatement profiles and navigate more crowded and complex airspaces before they get to cruise.
The issue is that they're required to take off from Ben Gurion airport before a certain hour to meet the nighttime curfew / noise abatement requirements. But that has the flight landing in SFO an hour before the customs and immigration desks open, and they're not allowed to open the doors until then.
Wish there was a way to make this particular flight a little longer...
I've been spending a lot of time watching ground ops from
http://www.airportviewer.com/airport/KSFO
(courtesy of HN, posted a few months ago). There are times when the planes pile up 14 deep. I saw JFK up to 20 planes on the ground waiting. This is hardly the airlines' fault.
What I dont understand is why they don't use wide-body planes more. I mean, I know the standard explanation: they use too much fuel on short-hauls. But why can't the manufacturer solve this problem, either by reducing the wing size or changing the shape, to have a wide-body, short-to-medium haul aircraft?
Aviation continues to grow, so while I understand the removal of hub-and-spoke, to the distributed pattern, it seems like if there's enough customer demand to run N 737's/A320's per day from SFO to, say, DEN, why not run 0.6*N 777's instead. Or what if southwest slowly replaced their '37 fleet with "short range 777s" ?
Or, more specificially, why don't they enact regulations at some of our busiest airports and say "Sorry, but at peak hours at JFK, you can only arrive/depart wide-body aircraft". Half the planes that run SFO are these tiny skywest embraer and bombardier jets. During peak times, restricting their use and requiring at least a '37 or a320 could boost capacity significantly (+100 people per takeoff/landing)
Not sure who are "they". FAA only cares about safety. Airport cares about profits. If tiny planes pay the same fee as large ones, why nerf them?
not true. Try flying a cessna into JFK. Apparently ATC just circle you over the atlantic until they "find time to fit you in". private pilot paid his taxes and "has every right to use the facility", but if you actually try it, you'll have a bad time.
Off the top of my mind, there are some other non-fuel factors
1- A competitive schedule in a business market includes offering a high number of frequencies, so running several flights on a narrowbody is preferred over a widebody
2- Building off of the above, you can segment your customers better, charging more for business-friendly timing
3- You mention seeing the tiny Skywest regional jets at SFO. While I'm not too familiar with United's route structure, I'd guess that most of these routes may not support a narrowbody (either because of mainline costs or demand)
4- Delta apparently used to run tiny regional jets out of JFK when Jet Blue was starting up in order to squat on slots, but also disrupt operations, since Delta would be much less impacted than Jet Blue.
I think we should revert to the hub and spoke system. Have huge jets that do nothing but travel between hubs all day. Let the business people have their half, and let the cattle buy essentially last-minute bus-tickets to traverse the country. Then book your ticket from the hub to home. Even though that's inefficient compared to direct routing, a 2 or 3 hour ground delay costs the same (in time) as going from CHI->LAX and then backtracking to phoenix or vegas to your final destination.
Another thing I think could work would be "JIT" routing. where you dont even know where your connections will be, until the day you fly. then you could have sudden, "ad-hoc hubs" that suit that particular day's distribution of travelers. Each morning a huge rack of computers could solve that day's "travelling-salesman problem" of weather, demand, location of aircraft, etc and come up with an optimal solution. people wouldn't like this at first, becuase of fear of the unknown, but I suspect it would lead to monumental increases in efficiency.
A similar analogy in computerland is how many of us are doing most of our computing on devices much less powerful than the ones we had ten years ago, a function of switching to mobile devices and high-overhead virtualized computing.
http://www.aerospaceweb.org/question/aerodynamics/area-rule/...
https://en.wikipedia.org/wiki/Drag-divergence_Mach_number
you want to be below or above transonic, and above transonic is banned pretty much anywhere.
The bottom of the drag curve is the speed at which the airplane will achieve maximum range for a given quantity of fuel; 76% of that speed will achieve maximum endurance. The distinction between range and endurance is that of distance versus time. Max range will get the most distance out of one pound of fuel, while max endurance gets you the most time out of that pound of fuel.
Many of the above hint at problems that provide uncertainty and doubt into Travelor itineraries but the discussed topic literally provides more certainty and assists with ensuring less missed connections.
There are some routes and airports that outside of expensive infrastructure cannot handle much more traffic. If you find out you made unreasonable promises you make them reasonable or try and make them possible.
Airlines are motivated to maximise fleet utilisation so the narrow focus on padding is a misleading and overemphasised element to judge the intent of this specific delay mitigation.
The industry is moving towards increasing collaboration, the article I think avoids mentioning the IATA recommended ACDM approach instead pitching a companies PoC from one of their sources.
Am I missing something? It's not like flights are spending more time in the air compared to before - it's just that you wait longer and your flight leaves late vs schedule. So how does that increase carbon emissions?
There's a lot of available info for US flight delays at bts.gov
One good example: https://www.bts.gov/topics/airlines-and-airports/understandi...
In most cases, aircraft get lined up in the sky in lanes. If your plane is nice and new and can move efficiently at a higher speed, it doesn't matter because it will get stuck behind an old crappy plane that cannot.
Unlike 50 years ago when there was little air traffic and airlines could pick the most direct route, today that is no longer the case. Flights are indeed longer because flying the most direct route or the route with the best tailwinds is no longer possible.
I’m surprised BBC didn’t do more fact checking.
Ryanair notoriously uses a very aggressive Cost Index for flight planning which favours absolute economy over speed, to the extent that sometimes ATC complains about their low cruising speed
More about CI: https://www.skybrary.aero/index.php/Cost_Index
In my nativity I had always assumed that airline do this to reduce fuel consumption by flying more slowly and hence reducing drag. :)
1) planes fly at a lower speed to save fuel
2) help airlines to claim they have improved on-time (OT) flight performance
3) it makes it easier to swerve the “magical three-hour limit” on delays – the threshold that qualifies passengers to file compensation claims at least under European Union passenger rights’ law.
It’s natural to assume that an N hour departure delay will cause you to arrive N hours late, and that your connections or other plans will be thrown off accordingly. However, that’s not often true—-schedule padding and changes in flight plans[0] often make up for some of the difference, though they often don’t tell you this until you’re in the air. It would be great if more gate agents could give you an expected departure AND arrival time during delays.
[0] I would not be surprised at all if the airlines explicitly trade off fuel costs vs. the costs of compensation. In other words, if you’re already late, don’t waste fuel try to make up all of the lost time, but use just enough to avoid a compensation-triggering delay.