I was recently on a KLM 747 where the cabin crew re-seated a passenger from upper deck to lower because they arrived by wheelchair. He was most unhappy but the pursuer was very firm on the issue.

I personally think this is a sensible policy - it may well be that she can move quickly when the circumstances need it, but having been on the evacuation slide of an upper deck 747 I would not want a frail lady go through that. It's a huge way up. Furthermore it's not just about her, it's about the people around her and whether they would be held up. Clearly some people should not be upper deck, and the wheelchair test seems very reasonable to me.

My other thought, and I direct this purely at myself, is that if I got to that age and had that degree of issues flying, I would probably want to not fly at all. It's only this generation that has had this luxury, humans have managed for aeons without being flung 6 miles through the air at 800 mph.