They do it at theme parks so why not the airport? All the theme parks I've been to have a "trial" seat outside each ride so that you can find out if it's safe for you to get on that ride. If we'll do it for rides that last maybe a minute then why the hell not for a journey that could last hours and put others lives at risk? If it was up to me then they'd just be banned from flying altogether! Even the whole "buy two seats" thing shouldn't be allowed as the seats are not designed to operate that way and it's dangerous! If you don't fit, you don't fly!! I'm not allowed to fly alone because I'm disabled and can't get off the plane by myself in an emergency. If I want to fly I have to have someone with me that is capable of getting me off that plane in an emergency. I can't help my problems but I'm still banned from flying unless I can meet strict criteria because I'm a danger to others if I fly alone. I totally accept that and it makes sense! If the airlines can refuse to let me fly for something that's not my fault though, why are fat fucks allowed to endanger others?