Got a boy who is about 400 pounds right now, I think he used to weigh close to 600. He's a taller dude, like 6'7" or 6'8" but still, massive.
When he used to fly coach, he would purchase two seats. Now he pretty much flies domestic first class. He flew to Europe, Asia, South America, etc. using business class.
He doesn't do any of this wheel chair craziness, dude walks through the airport at a fast pace, usually faster than most other people. There is really nothing crazy or different about his experience. He used to request a seat belt extender but no longer requires one.
Other than that, no one cares. I remember on a flight to Atlanta, he sat next to a chick and she was showing him nudes and letting him finger her.
This guy just seems like a body positivity weirdo, making a show of everything. Just get on the flight and reach your destination.