[wavemode]

Carry-on luggage is usually not weighed, there are simply safety margins in place for that sort of thing. (A human probably isn't capable of carrying a bag heavy enough to erode those margins.)

And fuel burn is the least of the concerns when it comes to weight - a far bigger issue is how it affects balance and engine lift. But on a plane the size of a jet airliner, this too is almost never a real concern when it comes to passenger weight - a standard weight is just assumed for each passenger and their carryon. (It's a concern for cargo weight, but that's why cargo is always weighed and balanced properly.)

Maybe if the airline notices that all the passengers are sitting on the left (for some strange reason) or something like that, they would reseat people.

[jareklupinski]

> Maybe if the airline notices that all the passengers are sitting on the left (for some strange reason) or something like that, they would reseat people.

I was on a turboprop plane when they made a few people switch seats to balance the weight: the seats were arranged Seat - Aisle - Seat - Seat , and all the singles on the left side were filled to the back, with only a few seats on the right side taken.