I wear what I am wearing to work, so business casual on Monday mornings, and Jeans with golf shirt on Friday afternoons.

When I do get upgraded on a Friday, I see a lot of people wearing what you would expect to see in a typical office on casual Friday.

I also see folks in T-Shirts, dirty jeans, and steal toed boots while carrying a hard hat. I think someone dressed like that belongs in first class just as much as anybody, especially if they travel regularly. They, like myself, probably go strait from work to the airport.