How do i make my ankles stop swelling while i'm on a long plane ride?

Wear support stockin: Wear support hose, get up every few hours and walk around a bit, consider taking an otc NSAID such as advil or aleve, (naproxen) avoid alcohol during the flight.

Compression socks: Or hosiery, excercise the feet and legs while seated by moving foot up and down ( doriflex and plantar flex). Finally, get up at least once an hour and walk the aisle.