context: The airport was built during the World War II of the region's race course (notified by Malta), when Gibraltar was an important naval base for Britain. Opened in 1939, the airport was only an emergency airfield for the Royal Navy Air Fleet. However, afterwards the runway was extended by reclaiming some land from the Bay of Gibraltar using rocks blown up from the Rock of Gibraltar while carrying out work on military tunnels. The last major extension of this runway allows larger airplanes to land in Gibraltar.
question: What year was Gibraltar Airport built?
answers.text: World War II