I think the only thing(s) this game needs is/are more helpful ally planes, and a like, a "throttle bar", as andyhu said, that shows how close you are to stalling. Pause and checkpoints would take away (some of) the challenge, and also make it EVEN LESS realistic. XD Its on a computer for gods sake, it can't get much less realistic than that.
@oscar: You're an idiot. Runescape is NOT the most popular MMORPG in the world. That would be, at least last time I check, WoW. Unless something has gotten over 12 million players since yesterday, it still is...