FL, with respect to your comment in an earlier post "I assume that an experienced Hunter pilot would be able to complete a loop by at least his entry height, probably higher.
Is my assumption wrong?"
In a Hunter (and similar types) the loop entry speed and technique during the first, upward half of a looping should guarantee that the aircraft will exit no lower than the entry height. Obviously, it can be misflown such that the exit height is below the entry height but then any manoeuvre can be misflown such that the aircraft crashes! Therefore, your assumption was totally correct.