[1][5] Prior to reforming at Luke in 1997, the 21st Tactical Fighter Training Squadron operated McDonnell F-4E Phantom IIs at George Air Force Base, California until 1993.

The 21st Fighter Squadron, 'The Gamblers', operate both the Block 20 F-16A/B and the F-16V for the Republic of China Air Force, under a three-year pilot training program called 'Peace Fenghuang' (Chinese for Phoenix).

This was the only squadron at Luke Air Force Base to operate the original F-16 variant, which are unusual in being 93 fiscal year serial new build Block 20 aircraft.

[6] After the end of combat in the Pacific, it remained on Okinawa as a part of the air defense and occupation force for the Ryukyu Islands after the war.

[6] Reactivated in August 1954 under Tactical Air Command and equipped with North American F-86 Sabres at George Air Force Base, California, the unit was re-equipped with the North American F-100 Super Sabre in 1956 and trained in operational proficiency as a Tactical Fighter Squadron, its aircraft carried a blue marking motif.

The squadron was inactivated on 15 March 1959 for budgetary reasons, its aircraft were reassigned to the incoming 31st Tactical Fighter Wing being moved from Turner Air Force Base, Georgia.

For students, the flying involves amassing fifty flights, starting with basic maneuvers to more advanced combat in both aerial engagements and bombing tactics.

Major Chen Hsing-ling, then commander of the squadron and later Chief of the ROC General Staff, came up with the idea to resemble the unit with the card suit of Twenty-One.