Airman
Airman was an enlisted rank used in the US Air Force during the 20th century on Earth. An airman basic wore no rank insignia on their uniforms and was also addressed as an "airman".

In 1968, two airmen basic assigned to the US 498th Airbase Group base in Omaha, Nebraska, accompanied Lieutenant Colonel Fellini in investigating a silent alarm that was accidentally triggered by James T. Kirk and Hikaru Sulu while they were attempting to retrieve tapes from the base. 

Later, while they were present during the interrogation of Kirk, the first air policeman was addressed by when Fellini asked him to "See what that is, Airman" when Spock knocked at the office door. ()

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Military ranks