s/deviously/optimally

I don’t care about the financial success of airlines but I sure as fuck don’t want jet fuel burned pushing around empty seats.

Sure you do. Airplanes should be at least 10% empty on average. High load factors are bad for the travellers.

If you want to save fuel fly 5% slower and save 10% fuel.

Are you saying maximizing load factors are worse for fuel economy or just slowing down would be a preferred cost saving measure in your opinion? Average load factor in the US is already <90%.

Either way, what about the unintended consequences for travellers if a slow down was mandated permanently?

You would need at least 15% more planes, pilots, ground personnel, etc... to handle the reduced bandwidth. For non-direct flights, fewer connections could be made likely increasing the airport population its ancillary services.

Airlines already do this from time to time usually when fuel costs outpaces pricing power:

https://www.reuters.com/article/airlines-fuelcells-kemp/refi...

When load factors get too high, recovery from irregular ops (weather, crew, or mechanical disruptions) becomes a nightmare for passengers. People end up stranded for days without available seats.

slowing down 5% adds 10 minutes flying time to a 3 hour flight. Drag varies with square of speed except when you get close to Mach 1 where it gets much worse.

Its also possible to fly 20% (36kft vs 30k) higher where drag for the same speed will be lower. Drag varies linearly with density.

An aircraft purposely designed for low fuel consumption could save 50% or more jet fuel without being significantly slower.

https://en.wikipedia.org/wiki/Aurora_D8

https://www.nasa.gov/topics/aeronautics/features/future_airp...

An 85% load factor still means you probably have a passenger sitting either side of you and a baby wailing somewhere in the distance, but now you're paying more money for your seat and arriving later.