FILE PHOTO: The US Army Avenger Air Defense System (AN/TWQ-1)

FILE PHOTO: The US Army Avenger Air Defense System (AN/TWQ-1) used to fire Stinger missiles is displayed with two test missiles during “Black Dart”, a live-fly, live fire demonstration of 55 unmanned aerial vehicles, or drones, at Naval Base Ventura County Sea Range, Point Mugu, near Oxnard, California July 31, 2015. REUTERS/Patrick T. Fallon/File Photo