The SIPA S.1100 was developed by the Société Industrielle Pour l’Aéronautique (SIPA) as a response to the French Air Ministry's requirement for a dedicated counter-insurgency (COIN) and observation aircraft. During the 1950s, French military experience in Indochina and Algeria highlighted the vulnerability of existing light liaison aircraft to small-arms fire, prompting a search for a rugged, armored replacement capable of operating from improvised airstrips. The aircraft was designed by Yves Gardan, starting around 1954–1955 under the internal designation GY-70.
Unlike many COIN aircraft of the era that were adapted from trainers, the S.1100 was purpose-built for its role. It featured a three-seat configuration for a pilot and two observers or gunners. To ensure survivability in high-threat, low-altitude environments, the design incorporated armor around the cockpit floor and engine nacelles, as well as self-sealing fuel tanks. The aircraft was heavily armed for its size, with planned internal armament options including two 30 mm DEFA cannons and four 12.7 mm Browning machine guns, or alternative configurations using 20 mm Hispano-Suiza cannons. Additionally, three under-wing hardpoints were designed to carry approximately 800 kg of rockets or bombs.
Power was provided by two Pratt & Whitney R-1340-S3H1 Wasp nine-cylinder air-cooled radial piston engines, each producing approximately 600 hp. The sole completed prototype made its maiden flight on 24 April 1958. While initial flight tests were promising, the program ended in tragedy just a few weeks later during a low-altitude demonstration flight. The prototype crashed, killing both the test pilot, Pierre Ponthus, and the second pilot, André Buthanet.
Following the crash, the French authorities terminated the S.1100 program. A second prototype had been started but was abandoned and never flown. The decision to cancel the project was influenced by the fatal accident, other failures of similar COIN prototypes like the Sud-Aviation SE.116 Voltigeur, and the availability of the American Douglas A-1 Skyraider on favorable terms. Consequently, the S.1100 never entered operational service, and no examples survive today.