The twentieth-century American air base from which Captain John Christopher was scrambled to intercept the Enterprise, and which Kirk and Sulu later infiltrated to remove evidence of the starship's visit.
The air base at Omaha, Nebraska features in the original series episode Tomorrow Is Yesterday. When the Enterprise is hurled back to the 1960s and appears in Earth's upper atmosphere, the base tracks it as an unidentified object and sends up an interceptor flown by Captain John Christopher, who ends up aboard the starship.
To erase the record of the encounter, Kirk and Sulu beam into the base at night to take the photographic film and tapes. An air police sergeant who surprises them is accidentally transported to the Enterprise, and Kirk is caught and questioned by the sceptical Colonel Fellini.
Spock, Sulu and Christopher return to rescue the captain, and the later slingshot manoeuvre around the Sun allows both Christopher and the sergeant to be returned before any of it happened.