Beginning in 2015, the US Air Force planned to retire all of its A-10 attack aircraft, but the plan was opposed by Congress. So far, the A-10 is safe even as the Air Force is planning to phase out more modern aircraft. The history of development of the A-10 Warthog dates back to the early 1970s, when the Soviet Union and its allies possessed an overwhelming number of main battle tanks compared to the US and NATO. The U.S. Air Force requested the development of a close-in, subsonic ground-support attack aircraft with a longer flight time. The A-10 Warthog, with its twin engines, subsonic speed, the main armament being a 30mm cannon and missiles and precision-guided bombs, proved to be a reliable and effective close-in ground-support aircraft in the battlefields of Iraq and Afghanistan.