Just saw the title (iphone cuts it off) Never mind my first post.

This isn't a good idea. You might get rebooked through another city, you can't check bags, and you could piss off the airline.

It's a violation of the small print on your ticket purchase and FF program.

One interesting thing though. I've been the last one to get on a plane and had my seat occupied and been told to just grab another one. Then I later find my miles missing and call in for them and get told I wasn't properly boarded and they fix it.

I've wondered if you could get away with a spin on that? I'm not up for it but I could see others on here trying.