Most of those fire retardant trousers and jackets are made of 100% cotton that is coated with some sort of powder. Not a good idea if you ask me, because that powder wears out with use, and cleaning.
If you're looking for something to train or fly by your own, or fly anywhere else except VIP transport - Nomex flightsuit is the way to go. It's not really expensive, you can buy them from military surplus cheap and in excellent condition. I bought one last year for 30USD, it was wared by some USAF Major...
once. Very comfortable when you get the right size
