I think you will find most airlines "official policy" says NO! BUT, having said that, there are always exceptions as circumstances dictate. I hold elite status on US Airways and was using a free ticket (coach) for travel to Jamaica. I went to check in and asked if I could use upgrade certificates to move up to FC even though I was on a free ticket. I guess the agent appreciated my honesty (that and there was probably a lot of space available in First that day) and I received the upgrade. On other occassions I have been told that I can not upgrade per company policy. No problem. Good luck...