 Man-portable air-defense systems (MANPADS) are shoulder-launched surface-to-air missiles (SAMs) that present a tremendous threat to both civilian and military aircraft.It is estimated 700,000 MANPADs have been built and sold across the world, thousands of which are unaccounted for and sold daily on the black market.The U.S. government says these type of weapons have been used in at least 36 attacks on civilian aircraft in the past three decades.