 During the 1950s, France became a major supplier of warplanes to Israel, but relations between the two countries deteriorated just before the Six-Day War, when France declared an arms embargo on Israel.Consequently, Israel Aircraft Industries (IAI) significantly increased its aircraft and weapons production (initially based on the French models) and Israel switched to the United States as its principal supplier of military aircraft.In three hours on the morning of June 5, 1967, the first day of the Six Day War, the Israeli Air Force executed Operation Focus, crippling the opposing Arab air forces and attaining air supremacy for the remainder of the war.