my daughter bought flight socks when we flew to Cuba last year, she smokes and was worried about the long flight, but they made her legs so uncomfortable she took them off somewhere over he Eastern seaboard.
so going to Antigua this last March she didn't bother wearing any, and so on the flight out, her legs swelled up and felt so tight she had to be taken to the cabin at the back and the staff made her walk back and forth and they put ice on her thighs, they were really swollen.
So we bought some socks in S Johns and she wore them home, it was uncomfortable but her legs were not painful or swollen.