The Civilian Airport was seen in many missions that involved any faction to send in reinforcements.
Campaign and Skirmishes only
The Civilian Airport is a garrisonable building and is usually found outside of heavily populated areas. It is used in the mission 4 by the USA in Zero Hour to bring in reinforcements. There are also usually small planes nearby that can be used by GLA Terrorists. During the Astana Riots and the capture of Baikonur Cosmodrome, the Americans were contacting for reinforcements, but were defeated at this airport in the GLA's third and seventh missions.