Lockheed Martin dominates the southwest corner of the airfield in Palmdale, which is known as Air Force Plant 42. Lockheed developed the master plan of Plant 42 for the Air Force in 1951, and was the first major tenant at Palmdale, building military aircraft and 250 commercial airliners here. From 1968 to 1984 Lockheed built L-1011s here, and provided space for its secretive Skunk Works division here even before that. Early Skunk Works programs include the U-2 spy plane, which was developed in Burbank, Palmdale, and at Lockheed’s secret test site at Groom Lake, Nevada, followed by the SR-71 Blackbird, and the F-117 stealth fighter/bomber. Lockheed Martin’s Palmdale operations continue to expand, and include eight principal structures, on nearly a square mile of land.