The Convair F-106 Delta Dart was the primary all-weather interceptor aircraft of the United States Air Force from the 1960s through to the 1980s. It was capable of Mach-2 performance and envisaged as a specialized all-weather missile-armed interceptor to shoot down bombers. It was designed without a gun and instead carried missiles in an internal weapons bay for clean supersonic flight. It served in the contiguous US, Alaska, and Iceland, as well as for brief periods in Germany and South Korea. In an effort to standardize aircraft types, it was replaced by the McDonnell Douglas F-4 Phantom II and McDonnell Douglas F-15 Eagle in 1981. "The Sixes" passed on to Air National Guard units and remained in service in various USAF and ANG units until 1988.