The 21st Fighter Squadron, 'The Gamblers', operate the Block 20 F-16A/B for the Republic of China Air Force (ROCAF), under a three year pilot training programme called 'Peace Fenghuang'. This is the only squadron at Luke to operate the original F-16 variant, which are unusual in being 93 fiscal year serial new build Block 20 aircraft. The squadron is to: Prior to reforming at Luke in 1997, the 21st Tactical Fighter Training Squadron operated F-4E Phantom IIs at George AFB, California until 1993.