A flying ace, fighter ace, or air ace is a military pilot who has shot down five or more enemy planes in aerial battle. The precise number of aerial wins necessary to formally qualify as an ace varies, although five or more are typically regarded to be essential. Some countries have different standards for what constitutes an "ace" because they don't want their best pilots lost when their opponents can afford replacements. For example, in the United States, pilots who shoot down four or more aircraft are considered aces. The term comes from the French word ailete, which means "with one wing". This refers to the fact that once a pilot has shot down his fifth plane, he has gone beyond being able to fight from the plane with only one side capable of movement. Instead, he must fly with one wing permanently affixed to his plane while the other flies the plane into safe territory where it can be repaired or replaced.