The company was formed on February 1, 1937, by the nationalization and merger of Lioré et Olivier, Potez, CAMS, Romano and SPCA.

[2] SNCASE incorporated the facilities of Potez in Berre-l'Étang, CAMS in Vitrolles, Romano in Cannes, SPCA in Marseille and Lioré et Olivier at Argenteuil and Marignane.

[2]) In 1941, during the Second World War, the Paris design bureaus of both the nationalized and the private aircraft firms were relocated to avoid capture.

[2]: 13 During the rationalisation of the nationalised Aircraft Industry during the 1950s, SNCASE merged with SNCASO to form Sud Aviation on March 1, 1957, which in turn was later amalgamated into Aérospatiale and eventually the Airbus group.

Most early Sud-Est aircraft retained their earlier designations, such as the Lioré et Olivier LeO 451 bomber.