industrian
will gently cradle you as time slowly ticks away.
QFT - work colleague has done it a few times with emirates, but his tip is this.
Always get there early (like way early) 1/2 an hour to an hour early to make sure you are the very first in line. Ask if there are any complimentary business class seats available for upgrade. If there are not, ask to be put on a waiting list for seats. Depending on who turns up, they may upgrade you. My work colleague has been upgraded twice as a result (on Emirates).
I have two medical certificates confirming my history of DVT and PE, and when flying in Asia they tend to at least get me a bump to "enhanced" Economy Class. In 2010 it allowed me to fly from Korea to Japan and then from Japan to Taiwan with free upgrades to business class. Hong Kong Airlines don't give a fuck though. There could be three people on the plane and you could have two broken legs and the flight attendants would still insist that you pay extra for an emergency exit seat.
Fuck Hong Kong Airlines.
When flying to Europe though, the European Courts determined a while back that European airlines aren't liable for DVT/PE so you can't play that above game with medical certificates. The last time around, KLM did give me an emergency exit seat and a lot of whisky though.
Speaking of which, the monetization of emergency exit seats makes me incredibly angry. I'm 6'5". If I'm obese then yeah, make me pay for two seats because I can go on a diet and exercise routine and lose that shit. I can't lose my godamn height, but still I have to pay extra.