To give its students a thorough understanding of the air-transport environment, ENAC sought to cooperate with the cole nationale de la mtorologie; a 29 May 1950 report noted the influence of meteorology on air traffic control and advocated meteorological training for air-traffic controllers.[20] Close links also traditionally existed between civil aviation and the Air Force. After World War II, as civil aviation was developing, members of the armed forces participated in its expansion. Pilots, radio operators, navigators and mechanics came from the military to the airlines, and ENAC sought to convert military aircrews.[20] On 9 June 1951, a memorandum specifying the school's responsibilities in the training of military pilots for civil aviation was signed. The university was the general contractor of operations, and provided theoretical training. In accordance with a of 31 March 1951 decree, the Service de l'aviation lgre et sportive (SALS) provided free flight training for pilot candidates coming from the army.[21]