Afghanistan has provided a reminder that, when you have a lot of unfriendly people running around with automatic weapons and portable anti-aircraft missiles, transport aircraft cannot get away with using their normal flying patterns. This is nothing new, it was discovered during the Vietnam war, and has continued to be a problem, as well as getting transports shot down, in places like Africa over the last two decades. In 1982, U.S. Air National Guard and reserve pilots set up a "defensive flying" course for pilots of tactical transports (mainly the C-130). The nine day course has increased in popularity since the war on terror began. During the 1990s peacekeeping missions in the Balkans, NATO transport pilots noted how vulnerable they were to hostile ground fire, and began sending their pilots to the course. The AATTC (Advanced Airlift Tactics Training Center) is for volunteers only and is conducted in St Joseph, Missouri. The course is held 16-20 times a year and has trained 1,530 crews so far. The crews spend about 45 percent of their time taking course in intelligence methods and planning missions into hostile territory. The rest of the time is spent in the air, where instructor pilots show how to fly low and use terrain to avoid being spotted, or shot at. These tactics also provide some protection from hostile fighters. Pilots also get to practice with night vision goggles. The course is very popular with pilots flying in support of special operations. In addition to C-130 pilots, crews for C-17, C160 and G.222 aircraft also attend. In the last year, a course was added to train ground crews on how to operate blacked out (not using any lights), to make it more difficult for nearby hostiles to shoot at them.