The 21st Fighter Squadron (21 FS) is part of the 56th Operations Group

56th Operations Group

The 56th Operations Group is a unit of the United States Air Force, and the flying component of the 56th Fighter Wing.The group is the direct descendant of the World War II 56th Fighter Group of the United States Army Air Forces...

 at Luke Air Force Base

Luke Air Force Base

Luke Air Force Base is a United States Air Force base located seven miles west of the central business district of Glendale, in Maricopa County, Arizona, United States. It is also about west of Phoenix, Arizona....

, Arizona

Arizona

Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...

. It operates the F-16 Fighting Falcon

F-16 Fighting Falcon

The General Dynamics F-16 Fighting Falcon is a multirole jet fighter aircraft originally developed by General Dynamics for the United States Air Force . Designed as an air superiority day fighter, it evolved into a successful all-weather multirole aircraft. Over 4,400 aircraft have been built since...

 aircraft conducting advanced fighter training for the pilots of Republic of China (Taiwan).
The 21st Fighter Squadron, 'The Gamblers', operate the Block 20 F-16A/B for the Republic of China Air Force (ROCAF)

Republic of China Air Force

The Republic of China Air Force is the aviation branch of the Republic of China Armed Forces. The ROCAF's primary mission is the defense of the airspace over and around Taiwan...

, 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.