Air Station

The Washington, D.C. airport was an airport before the bombs fell.

Background
Some time after the bombs fell, a group of people trying to gain entry to Vault 101 used the scrap from the planes and buildings at the airport as building materials to create the town of Megaton. Over time, the rest of the airport was reclaimed by nature; no sign of its existence remains.

Appearances
Washington, D.C. airport is mentioned in Fallout 3.

Behind the scenes
According to Manya, the airport was not far from Megaton; it could be Ronald Reagan or Dulles airport. Neither actually appear in the Capital Wasteland.