@whitequark arguably a far better metric for the denominator in that calculation would be the number of bags you took. mean passenger mass probably doesn't vary that much for any given route, whereas bag count is probably a fairly accurate proxy for 15-20 kg of carried mass each.

@whitequark although even then the calculation has major uncertainty factors for reasons you don't even control as a passenger, like "did the flight sell out?" (since you're then dividing the constant mass of the aircraft by fewer passenger)

@whitequark yeah true. it's the fuel to carry the fuel problem

@whitequark @gsuberland a question i am asking from a place of total ignorance and curiosity: do commercial airlines vary the amount of fuel they take based on the total weight of the boarded flight and expected distance?

they keep finding ways to pack flights fuller and fuller (at least in the merica), which goes against how i would expect cost optimization to work unless they were being really wasteful with fuel to begin with

@aeva @gsuberland

a question i am asking from a place of total ignorance and curiosity: do commercial airlines vary the amount of fuel they take based on the total weight of the boarded flight and expected distance?

yes, this is a really important factor in the pre-flight calculations and getting it even a few % off can have serious consequences

@aeva @whitequark all of that, plus weather.

@aeva @gsuberland

they keep finding ways to pack flights fuller and fuller (at least in the merica), which goes against how i would expect cost optimization to work unless they were being really wasteful with fuel to begin with

don't forget that airlines often lease most of their planes rather than outright owning them (and even if they own it they took out a loan first), so any idle seats or idle planes cost them a lot of money regardless of fuel

@whitequark @aeva @gsuberland what i'm more curious about is if they use counts of pax/bags or if they use some kind of sensors in the landing gear to get actual weight.

When you're flying little single engine stuff it's common to actually weigh everyone and bags to make sure you're not too unbalanced

@azonenberg @whitequark @aeva airlines and safety bodies rely on "Standard Passenger Weight" studies for the passenger part. baggage is weighed.

the figures include uncertainties.

@azonenberg @whitequark @aeva @gsuberland I have had a flight tell passengers (after boarding) that they were going to offload some luggage for weight reasons so they do have sensors as well, apparently.

@wronglang @azonenberg @whitequark @aeva it's measured at check-in. they were probably offloading because they sold based on median luggage weight and your flight happened to be an outlier on what people actually arrived with.

@wronglang @azonenberg @whitequark @aeva like the baggage allowance is 23kg or whatever but they assume the average bag on any given flight is lighter than that 'cos designing the limits around the upper bound is inefficient. if everyone shows up with 21-23kg bags then it's too much, but that's really rare.

@gsuberland @azonenberg @whitequark @aeva huh, I would've assumed they'd do that before boarding but 🤷

@wronglang @azonenberg @whitequark @aeva they don't usually finish loading bags until they're already boarding. plus until everyone's boarded you don't know how many people no-showed.

@gsuberland @azonenberg @whitequark @aeva yeah that makes sense, funny to have just inferred that wrong

@azonenberg @whitequark @aeva obviously it's not globally static - average passenger mass in Texas is gonna be very different to Singapore.

@gsuberland @whitequark @aeva checked, i assume you mean? i've never had anyone weigh my carryon

@azonenberg @whitequark @aeva yeah checked. since carry on is restricted you can assume a fixed upper bound per passenger.

@gsuberland @azonenberg @aeva oh right they probably do it when you check it in

@whitequark @azonenberg @aeva yeah check in bag weight is how they measure that part