A wingman (or wingmate) is a pilot who supports another in a potentially dangerous flying environment. Wingman was originally a term referring to the plane flying beside and slightly behind the lead plane in an aircraft formation.
According to the U.S. Air Force,
The traditional military definition of a "Wingman" refers to the pattern in which fighter jets fly. There is always a lead aircraft and another which flies off the right wing of and behind the lead. This second pilot is called the "Wingman" because he or she primarily protects the lead by "watching his back."
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