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Comment by delta_p_delta_x | Hacker News Reader

> Flight times between Singapore and London would be cut from 18 hours on conventional aircraft at the time to just 10 hours.

This is very interesting, because current Singapore-Heathrow direct flights are around 13 hours. I wouldn't pay first-class++ fares for a 3-hour flight time reduction in a tiny, cramped cabin with worse pressurisation and ventilation than first class on modern A380s, B777s and A350s that currently ply the route.

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Currently there are aircraft able to fly that distance without stopovers. That wasn't the case in 70s, including Concorde. Modern version of Concorde that would have the necessary range for that flight would do Heathrow to Singapore in 5-6 h.

Routing in the 1970s (and until at least 1992) would also likely have been far longer, with most Soviet and Eastern European airspace closed to Western flights.

Whether the lack of non-stop service was on account of routing and range or of lack of sufficient travel demand I don't know.

Current routing appears to traverse Pland, Ukraine, Russia, Georgia, Afghanistan, Pakistan, and India. I could see much of that not being advisable in the 1970s.

<https://www.airportia.com/flight-img/7760680/sq308-sin-lhr-s...>

Plenty of that isn't advisable now. I flew Frankfurt to Singapore at the end of 2022 and we flew over the south side of the Black Sea to avoid Ukrainian and Russian airspace. We also avoided Afghanistan and flew over Iran instead which slightly surprised me.

Looks like London-Singapore flights do the same

https://www.flightradar24.com/data/flights/sq305#3437e32f

It's less the airlines being cautious (like they finally started being over Ukraine, but not until MH17): Russia has just closed their airspace to most Western airlines (and vice versa).

This leads to sometimes quite extreme differences in travel times between two cities depending on whether a Western or e.g. Chinese airline are conducting the flight (e.g. London-Shanghai), since Chinese airlines can still overfly both Europe and Russia.

Singapore Airlines (who I flew with) wasn't barred from Russian airspace but they have decided to voluntarily avoid it.

Another thing into play are the airspace fees. It’s a substantial income for Russia. It’s possible that some airlines estimate that they are too high, just out of economic factors and not political factors.

https://simpleflying.com/russia-overflight-charge-hike/

They skyrocketed (pun intended) by 20% just in 2023, amount to $1.7bn and are justified by the radar and route operators, and by the …security provided by the Russian army.

After downing the MH317, many airlines avoided the Ukrainian airspace… in profit of the (unavoidable?) Russian one, further benefiting Russia for this horrible crime. Killing those people may even have provided more revenue to Russia.

Oh yes, a while ago the Chinese airline Air China wanted to fly from New York to Beijing over Russian airspace (the shortest path does involve Russian airspace) but the U.S. government prohibited them from doing that as a matter of fairness. The end result is that the Chinese airline had to operate a domestic flight from New York to Los Angeles in order to fly to Beijing. https://viewfromthewing.com/air-china-has-filed-to-fly-new-y...

> The end result is that the Chinese airline had to operate a domestic flight from New York to Los Angeles in order to fly to Beijing.

This isn't unheard-of. Qantas does (or used to) do this as well, running SYD-LAX-JFK, for efficiency reasons.

Cabotage laws prohibit 081/CCA from carrying any passengers on the domestic leg of that route except the ones that are booked on the international leg of the journey as well. So it's not like you can just book a flight with them domestically.

This concept is called "freedoms of the air" in case anyone is curious about learning more: https://en.wikipedia.org/wiki/Freedoms_of_the_air

    It's less the airlines being cautious
    (like they finally started being 
    over Ukraine, but not until MH17)

You are misrecalling the chronology. Some airlines such as British Airways were avoiding that airspace before MH17 was shot down, it was making the news beforehand. Other airlines such as Malaysia Airlines continued rolling the dice on flying in an active warzone.

What changed after MH17 was that avoiding it was mandated by the relevant authorities.

That's clearly not the actual route aircraft are taking since it flies directly over the warzone in eastern Ukraine.

"Appears" is doing some heavy lifting in my comment, and was there for a reason.

If you know of a more representational route I'd appreciate your sharing it. My previous link was based on a search for London-Singapore air routes.

Hrm ... I suppose FlightAware or FlightRadar24 might show this, and yes, it does.

BA21 seems to fly over Russia per FlightAware:

<https://www.flightaware.com/live/flight/BAW21>

SIA308 flies a more southerly route, crossing the Black Sea and Turkey rather than overlying Ukraine, and conspicuously avoiding Afghan airspace:

<https://www.flightaware.com/live/flight/SIA308>

> BA21 seems to fly over Russia per FlightAware:

"ARRIVED OVER 11 YEARS AGO"

Good call, I was relying on a search for flights and didn't check to see if that was current.

BA11 seems to be among British Airways current LHR->SIN offerings. Here's yesterday's flight path, which largely resembles Singapore Airways. Flight time 13h15m.

<https://www.flightaware.com/live/flight/BAW11/history/202403...>

> Current routing appears to traverse Pland, Ukraine, Russia, Georgia, Afghanistan, Pakistan, and India. I could see much of that not being advisable in the 1970s.

When I flew from Helsinki, Finland to Hong Kong this summer, the plane avoided flying through Russian airspace, so not sure it's much better now than in the 70s, for some routes at least.

"Avoiding Russian airspace: From a shortcut to a detour" - https://www.finnair.com/en/bluewings/world-of-finnair/avoidi...

> On Monday 28 February 2022 Russia closed its airspace as a countermeasure to EU airspace closure. This meant many changes to Finnair’s Asian services, as most of Finnair’s flights between Europe and Asia have used the shortest, fastest, and most environmentally sound route over Russia.

Given russias current trajectory with their war of genocide against Ukraine[0], it is not foreseeable that any western commercial airlines would be able to fly in their airspace for years to come[1].

[0]https://en.wikipedia.org/wiki/War_crimes_in_the_Russian_inva... [1]https://www.npr.org/2023/03/18/1162659715/russian-53rd-anti-...

That's just marketing image some graphic designer made.

For the actual current route, check the flight tracking services like this: https://planefinder.net/data/flight/SQ305/history/4-48720917

So, it's UK->Belgium->Germany->Czechia->Austria->Hungary->Romania->Bulgaria->Turkey->Iran->Pakistan->India->Malaysia->Singapore

But Concorde was able to fly fast only over the uninhabited surface like ocean. And on the route from London to Singapore how much of that? A third?

Only a small portion of the direct route flies over the Indian ocean, the rest is basically over land:

https://www.airportia.com/flight-img/7760680/sq308-sin-lhr-s...

I remember, when I was a kid, hearing a thunderous roar and rushing outside, and saw the Concorde with the Singapore Airlines livery, flying overhead. Left an impression. Not the usual flight path, as I was living in the central part of Singapore at that time. Assuming it was an one-off for testing purposes.

Is it more economical to carry all that weight in fuel versus having stopovers?

Or is this a tradeoff of time versus climate, where time won?

Refueling is very wasteful - that's why so many flights are direct today - because it's much cheaper.

I'm sure that's true although I don't know how the numbers pencil out. That said, people also much prefer non-stop flights because of time, hassle, and reduced likelihood of something going wrong.

That's not quite true AFAIK at least a couple of years ago the super long routes (18+h) were served in business class only because not enough customers wanted to do such a long flight in economy.

That's mostly not true as far as I've seen because most trans-pacific flyers are not willing/able to spend thousands of additional $ to fly in business class.

Another factor besides comfort is that they can extend the flight time 1-2 hours by having fewer passengers and bags onboard, which of course means premium seats like SQ23/24.

Qantas is planning to launch 18–21 hour routes in 2026 with economy class, using modified A350-1000 with an extra fuel tank in the hold.

Are you talking about "Project Sunrise"?

https://en.wikipedia.org/wiki/Kangaroo_Route#Project_Sunrise

The Singapore Airlines Singapore to New York flight is 19 hours and only has premium economy and business. I have to make this trip fairly often and I prefer to take the direct flight as it’s simpler, faster and I have to pay extra for leg room either way. That said, if I had the means I would take business each time, because 19 hours in even the nicest economy seat can be tough.

It's also riskier to do fuel stops en route. Most accidents happen on takeoff or landing.

Accidents, and maintenance - much maintenance is predicated on cycle times, i.e. how many take offs and landings (and others are based on operational hours).

Depends on distance, cargo is best way to look at the ranges. As they optimize for cost per nautical mile. Not passenger demand or comfort or speed. At certain point refuelling saves in cost.

That becomes the main issue, the Concorde as it was had 26,400 gallons <=> 95,680 kgs of fuel, and would need more than double that (likely) to do the flight in one go (bar major improvements to efficiency, and counting that more weight at takeoff needs more weight of fuel to fly that extra weight).

A quick search says about 40 minutes to refuel a jet, so a stopover is going to add at least an hour, probably more because they have to come out of supersonic, etc.

And how are these numbers in subsonic flights?

A flight from London to Singapore. How much fuel would it need without stops, versus how much fuel in the least-fuel case (but more-stops case)?

One thing to take into account is that landing and taking off is very wasteful with fuel - jet engines use significantly more fuel when running in dense air and that doesn't include increased power for climbing.

I'm sure there's someone who can plug in numbers into a flight planner here, I'm interested in actual numbers.

OK, sure, I plugged this into a sim flight planner (http://onlineflightplanner.org/). This is on a Dreamliner.

    Heathrow - Changi: 63933 kgs
    
    Heathrow - Tehran: 26957 kgs
    Tehran - Changi: 39580 kgs

So at least based on this it's not too much of a difference, only 4% more with a stop. (Tehran looked to be roughly in the middle on the flight plan between London and Singapore.)

Interesting, I'd expect it to be a larger difference considering how much the carriers avoid stopovers.

Maybe the fees and organization of refueling tips the balance?

Carriers don't want to do a stop unless they're offloading and onboarding passengers, so they'd rather run one flight to the intermediary, and another direct.

Well yeah, we're talking a about WHY it's a problem for them to stop.

IIRC airframe lifetime is rated in pressurization cycles.

It adds a surprising amount of time. You have to descend, land, taxi to a fueling area, refuel, taxi, take off, climb. And that's if the local regulations allow fueling with passengers on board.

That's probably around 2 hours extra. And this in turn can require the plane to carry additional pilots and flight attendants.

Is this also assuming the "modern Concorde" wouldn't do a sonic boom and could therefore fly supersonic over land?

Hmm I wonder. A modern Concorde might be more spacious and better pressurised but much faster than Mach 2 is going to be very difficult due to higher speeds needing incrementally more energy and generating more heat.

Supercruising at Mach 2 is a huge accomplishment and I don't think there's any aircraft in operation that can still do that. Jetfighters can do it while afterburning but it is impossible to reach Singapore that way.

I just don't see a supercruising aircraft being possible at Mach 3.

The speed gains would be due to lack of stopovers, assuming higher range, not due to higher airspeed.

Ah I see. True, a lot of advancements have been made in fuel efficiency indeed. Sorry I misunderstood your comment.

I'm not clear what you mean by "better pressurised"? If you mean the cabin altitude, one of the advantages of Concorde was that the cabin had a lower cabin altitude than other airliners, then or now.

Concorde cruising supersonic on dry power was apparently due to the variable intake ramps (https://www.heritageconcorde.com/air-in-take-system), which presented compressed subsonic air to the compressors at supersonic speeds, bypassing excess air. This reduced the work that the compressors had to do, avoiding the surge issues with the J-58 which the A-12 family of aircraft ran in to. There is probably a bit of stretch there, as Concorde was limited by airframe temperature, but the temperature of the compressed intake would probably be the next limitation. As far as I know, Concorde was the only supersonic-native aircraft, with best range being achieved at M1.4.

What _was_ the routing and speed? That was my very first question and the blog post doesn't really answer it. How much of the flight was supersonic? They talk about avoiding India for the BAH-SIN leg, and trouble over Saudi Arabia, but there's a lotta populated land between BAH-LHR. The flight listing says this:

    SIN-BAH: 3698 miles, 4 hrs  6 mins, Mach 2.02 cruising speed
    BAH-LHR: 3120 miles, 4 hrs 21 mins, Mach 2.02 cruising speed

Those numbers just don't make sense. That's 130 miles short of the great circle distance from SIN-BAH of 3935 miles. And then they talked about adding another 200 miles to go around India. So assuming the flight time itself is accurate, that leg should be:

    SIN-BAH: 4135 miles, 4 hrs 6 mins, Mach 1.3 average speed

But how much of that time _could_ be spent at the listed cruising speed? Mach 2 will travel 4135 in miles in just over 2.5 hours! So we're looking at less than half the flight spent in supersonic — and this is the leg that's mostly over the Indian Ocean.

The BAH-LHR leg is even trickier.

Anyhow, it's little wonder that a direct non-stop is near the Concorde's time with these restrictions and the refueling stop.

> Those numbers just don't make sense. That's 130 miles short of the great circle distance from SIN-BAH of 3935 miles.

In an aviation context, those are most likely nautical miles (equivalent to 1 minute of a degree in north-south direction, which is why 10,000 km (initially defined as the distance from the equator to the pole) is basically 5,400 NM (90 degrees from the equator to the pole, times 60 minutes/degree)) rather than statute miles, which are some certain number of yards and feet in that quaint customary system used still used by some people in the USA, Liberia, and Myanmar.

Indeed, according to the interweb, the distance between Singapore (Singapore Changi Airport) and Manama (Bahrain International Airport) is 3935 miles / 6333 kilometers / 3420 nautical miles.

Aha, of course!

OK, if those are nautical miles this does make much more sense — 3698nm is 280 nautical miles (320 miles) longer than the great circle route. It's a bit longer than the naive calculation I made — increasing the average speed (and time at cruise) a little bit, too.

Then the BAH-LHR leg is more interesting too — its great circle route is 2754 nm, so they're going 366 nm (420 miles) out of their way. Their listed distance is approximately what it'd be if they routed through the Mediterranean over Malta.

https://www.greatcirclemap.com/?routes=BAH-LHR%2C%20BAH-MLA-...

In 1972 it was stops in Bahrain, Bombay, Rome and Frankfurt, and first class on that plane was no better than first class on concorde.

https://simpleflying.com/singapore-london-50-years/

Yeah but you're talking about an aircraft that first flew 55 years ago (almost to the day).

The cabin cross section wouldn't change so if the Concorde was designed today.

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