In cooperation with the CEV (Centre d'Essais en Vol), the government flight test center and ONERA (Office National d’Etudes et de Recherches Aérospatiales), the French aerospace lab, Aérospatiale modified a Canadair/Lockheed T-33AN into a supercritical wing research testbed. Since 1972 Aérospatiale had been engaged in the study of a subsonic supercritical wing for civilian use (ostensibly for the nascent Airbus Industrie). The T-33 which was used by the Armée de l'Air at the time for flight training was dubbed the Pégase which was itself an acronym that stood for Programme d'Etude Générale d'une Aile Supercritique Epaisse, or "Thick Supercritical Wing General Study Program".
A supercritical wing would have allowed an increase in flight performance across a wide range of subsonic speeds and despite being a thicker wing, it would have allowed for a higher Mach cruising speed. In jetliners, a supercritical wing holds more fuel due to its thickness without sacrificing high speed cruising speeds yet low speed performance will also be enhanced.
Using balsa, textiles, and resins, engineers reshaped the Pégase's wings into various supercritical profiles. It made its first flight on 13 April 1977 with Alain Guillard at the controls and it would go on to make 74 test flights with its last flight on 2 May 1978. During flight testing, the straight-winged Pégase was able to cruise in level flight at Mach 0.8. The Pégase was never returned to its original configuration and is presently in storage at Le Bourget in Paris awaiting restoration for display.
Source: Wings of Fame, Volume 16. AIRtime Publishing/Aerospace Publishing, 1999, "T-Birds and Silver Stars: Lockheed T-33/T2V Variants by Robert F. Dorr, p123.