Fat people should have to buy 2 seats on an airplane

https://lemy.lol/post/56423131

I feel like this is a fairly common opinion. Also, I believe they do have to after some point; not sure how the airline decides though?
It’s got to do with calculating the amount of fuel for the plane. More weight requires more fuel.

I mean, mass is a massive factor for flight.

If you ever fly on a small plane, they ask for your weight, and cap your luggage weight because it is a requirement to not crash.