I had never considered altitude as a factor in takeoff weight limits.
How much load would a typical FedEx flight need to shed to operate out of Denver?
How much load would a typical FedEx flight need to shed to operate out of Denver?
Next time you're flying out of Denver, notice how long the takeoff roll is. When my father flew jets out of Denver, he'd hang the tailpipe over the back edge of the runway so he'd have every last foot of runway to get airborne.
The 737 has better performance with high-altitude takeoffs.
Checked luggage is weighed when you drop it off, so presumably the exact weights are available to the pilots. For passengers themselves and their carry-on baggage, accurate weights aren't available so statistical averages are used, based on the number of passengers and their baggage allowances.
Airliners do have "squat sensors" in the landing gear, but they're not capable of accurately measuring the aircraft's weight. They're just binary-valued sensors that check whether the gear struts are under stress, to prevent the gear from accidentally being raised while the plane is on the ground.
There has been at least one crash due to mis-estimating the weight of the passengers + luggage + cargo. A strain gauge on the struts, even if inaccurate, could provide a backup sanity check for the weights.
So, yes, FedEx did think of having sensors, of some kind, in the landing gear.
But I never heard more about such sensors, and, for the times I rode the jump seat in the planes, I never saw pilots working with weight and balance from data from the landing gear.
Maybe later, after I went to grad school, FedEx did do something with such sensors.
So, right, the sensors are a good idea and were considered and, maybe, eventually implemented.
But, yes, hot air at high altitude hurts jet engine thrust, a LOT.
There's a leg connecting Tokyo and Mexico City. The Tokyo flight goes direct to Mexico City however the Mexico City flight stops in Hermasillo on the way to Tokyo.
Due to the higher altitude of Mexico City, it takes more fuel to get off the ground and requires a pit stop in hermasillo to get all the way to Tokyo.
Disclaimer I'm only partially sure that I'm remembering the whole story correctly.
Every couple of years, there'll be a day or two in summer when temperatures at the airport in Phoenix get above the maximum takeoff temperature for a lot of the smaller regional jets, and chaos ensues as all those flights (it's a US Airways hub) delay or cancel.