I'm 6'2" and my knees used to be painfully squeezed into seats and everything was incredibly uncomfortable on flights. At the time I weighed 275lb. I've since lost weight and I was surprised how much more comfortable flying is.

You wouldn't think being obese would impact knees not having enough space, but my ass shrank in multiple directions and I have about four to five inches of free space now between the seat in front of me and my knees. Unless you're much taller than I am, it's likely that losing weight will not just help with your health, but make flying more comfortable.

If you are taller, well, life sucks for us tall people in many ways and we can't expect airlines to build comfortable seats for people two or three standard deviations beyond the normal height.