I just had the worst flight of my life.

On a UA flight from EWR to MIA I had a middle seat next to my gf. She had the window seat. It was on Economy Plus so there was enough leg space, and it looked like a nice 3-hour flight.

Until this REALLY fat person set next to me (in the aisle seat). He was so big that he could not sit in his seat unless the arm-rest was up. He asked me if he could lift it, and I said sure (I had no idea what followed or that he was so big).

Well all of a sudden, he is taking 20-30% of my seat. I had to cramp next to my girlfriend just to be there. The fat person (to be fair) asked the FA if he could be seated somewhere else, but she said the plane was full and she couldn't do anything (it was indeed full).

I wondered if I should make a fuss or not, but on the other hand I wanted to get to Miami. During the flight my legs "felt asleep" because they were pressured so much, so I had to move quite often in the seat to make sure I got the proper circulation. I couldn't really do anything properly - impossible to sleep in such a position, or to use my laptop. Even the tray table could barely be there.

I survived this terrible flight, but I am wondering what you guys would have done. If I experience anything that could cause such a flight again, then I'd rather step out of the aircraft and be rescheduled than go through this again.

1. Should I politely just have refused when the fat person asked whether he may lift the armrest? (if I had done so, there is no way he could sit there, so then maybe this would give HIM a problem rather than me).

2. Given that there is nothing to do and FAs say the flight is full and there is no more extra space, and the fat person does not want to be rescheduled, should I then demand to be taken off the plane with my girlfriend and rescheduled? Would UNITED accommodate this for both of us?

3. Is it at all legal to be seated like that? In case of an emergency, there is no way that our row could evacuate quickly because of the fat person.

4. How would you guys handle it? Would you really make a big thing out of it and not accept what I have been through, or would you just try to survive it?