When I was in the service the stewardesses would try to put us in first class if there was room. So I’ve flown up there several times. Korean Air Lines was by far the best.
Lucky you!
I have had that happen once, and that was because I was supposed to have a guaranteed seat on the plane, but the only open seat was in first. Otherwise, I fly back with the rest of the cattle.
I know someone who pays out of his pocket to get an upgraded seat, if any are available. I just take the cattle car seats that the government pays for.