Agreed. My rear dropouts are over that dimension. The shortest dimension of the bars and the rear hub might each be over that and stacking it all together in a case or bag would certainly be.

On the notion of carrying on a bike, I have to wonder if the OP is pulling our collective legs or just hasn't really thought this through. The overhead compartments I have seen wouldn't fit a typical bike wheel, let alone the rest of the bike..

Flying domestic US flights, pick your airline based on their bicycle policy. Frontier and Southwest have been pretty bike friendly in the past when I used them. I drove to my last couple trips so it has been a while since I checked, but their rates were reasonable when I used them.