If you were trapped in a burning aircraft, then you will toast. A nomex suit will give you a bit of protection, but it is just flame retardent, and that is it.
A mate of mine ejected from a burning Jag after a mid-air. The soles of his boots were melted, and his badges got burnt off. But the suit, and the bits of his body covered by the suit were fine. He wasn't in the aircraft for more than a few seconds after impact though.