The Fairchild AU-23 Peacemaker is an American armed gunship, counter-insurgency, utility transport aircraft developed from the Pilatus PC-6 Porter for the United States Air Force.

In May 1971 the Aeronautical Systems Division at Wright-Patterson Air Force Base, Ohio, began work on a project to evaluate the potential use of armed light utility short takeoff and landing aircraft in Southeast Asia.

The program, named Credible Chase, was designed to add mobility and firepower to the South Vietnamese Republic of Vietnam Air Force (RVNAF) in a relatively short time.

Initial performance testing was conducted with leased aircraft at Eglin Air Force Base, Florida, and was successful enough to warrant a combat evaluation.

Specific problems identified included a slow combat speed (135 knots (250 km/h)), a low working altitude, no capability for "zoom" escapes after delivering ordnance and a complete lack of armor protection for the crew and vital aircraft systems.

[1] Royal Thai Air Force 501 Sqn AU-23A JTh2-20/19 coded 42079 (former FY 74-2079) crash-landed in Khlong Hoi Khong district around noon on 5 March 2019.