I am a couple of thousand miles short of a free upgrade on CO. During my next trip I'll pass that figure on the 1st flight. Each of the 4 flights (a pair each way) are lengthy 3,500 mile treks. I'd like to upgrade one of them but if I remember correctly, you're supposed to apply beforehand. Obviously I'll be away and won't be able to do this... or will I? Is there a way around this?