The way that they put it is that if you can put the armrests down and buckle up (with one seat extender, if needed) and not "encroach" on the other person's space, you're good. Basically, if you can sit in a seventeen-inch wide seat with armrests and not have your belly spill over or anything, you're fine. The flight attendant can actually pull you off the flight after you've been seated, even if you're sitting next to your DH and he's not complaining. Considering how many Americans are fat, you'd think they could have larger seats on a plane. Good luck with the weight loss. I'm gonna try, but I'm going to buy the second seat anyway, just in case. I don't see myself losing enough weight to be under what I was when I moved back by the time that I go down.