FORT WORTH, Texas, March 19, 2013 /PRNewswire/ -- Four Lockheed Martin (NYSE: LMT) F-35A conventional takeoff and landing (CTOL) aircraft were officially welcomed by the U.S. Air Force Warfare Center at Nellis Air Force Base, Nev. during a commemorative ceremony today. The jets are assigned to the 422 Test and Evaluation Squadron of the 53rd Test and Evaluation Group. "For more than 50 years, it's been our privilege to support the Air Force mission, and we're honored to deliver the first four F-35A CTOL aircraft to Air Force Warfare Center," said Orlando Carvalho, executive vice president of Lockheed Martin Aeronautics. "The work done by the Nellis team will forge the F-35 into the fighter of the future and test it to its limits. Their skilled pilots and maintainers will take the F-35's performance to new heights and define the tactics the F-35 will one day use to defend freedom around the world." The first four operational-coded 5 th generation F-35A CTOL fighters to Nellis marks the beginning of operational testing and evaluation at the base. To date, 24 CTOL aircraft have been delivered to the Air Force and 58 aircraft to the Department of Defense. The 422 nd TES is a composite squadron that executes Operational Test & Evaluation for the F-35. The squadron conducts tactics development, foreign materiel exploitation, and special access programs to optimize system combat capability. By 2019, a total of 12 F-35As will be assigned to the base for testing and evaluation. The F-35 Lightning II is a 5 th generation fighter, combining advanced stealth with fighter speed and agility, fully fused sensor information, network-enabled operations and advanced sustainment. Three distinct variants of the F-35 will replace the A-10 and F-16 for the U.S. Air Force, the F/A-18 for the U.S. Navy, the F/A-18 and AV-8B Harrier for the U.S. Marine Corps, and a variety of fighters for at least ten other countries. Lockheed Martin is developing the F-35 with its principal industrial partners, Northrop Grumman and BAE Systems.