NATO E-3 AWACS aircraft flew their last mission over Afghanistan in September 2014. Since 2001 American AWACS have been available in Afghanistan and still are. NATO AWACS arrived in northern Afghanistan in 2011 to mainly handle the growing number of NATO transports and warplanes operating up there. In three years these AWACs flew 1,273 operational (as opposed to training or administrative) sorties, average about ten hour each.
Although there are not a lot of military, or civilian, aircraft operating over Afghanistan, there are few civilian radars on the ground to keep track of things overhead. So the AWACS helped out with this as well as making sure military aircraft, especially the aerial tankers and the aircraft seeking to refuel, could easily find each other. Occasionally there was a major operation that put a lot (a dozen or more) aircraft into a relatively small area and the AWACS were in their element with that. AWACS could also watch out for smuggler (of weapons, terrorists, drugs or whatever) aircraft.
The experience in Afghanistan was based what had happened in the 1990s. During its first wartime workout, during the 1991 Gulf war, the AWACS proved its worth, often in more ways than anticipated. The use of over a hundred tankers to refuel combat aircraft would not have been possible without the AWACS being there to efficiently link tankers and aircraft needing fuel. Forming up the Wild Weasels (electronic warfare aircraft), and coordinating their use with the bombers they escorted, was much easier using an AWACS. Just keeping track of who was who and going where would not have been possible without the AWACS. The communications equipment on board an AWACS allowed information gathered by one AWACS to be quickly shared with other AWACS in the vicinity, other combat aircraft in the area as well as units at sea or on the ground. This function, which was eventually made to work, gave generals and admirals the goal of trying to link together all the sensor and communications of every ship, aircraft, and ground unit in the area. But first, an AWACS for ground operations was needed.
The Gulf War experience was immediately put to use during the Afghanistan war and insured that the bombers, and the aerial tankers that kept everyone flying, were always where they were needed. This was later repeated in the 2003 Iraq war. This sort of thing doesn't make the news but without AWACS a lot of those newsworthy bombs would have never made it to their targets.
E-3 AWACS development began in the late 1960s, and the first prototypes were flying in the late 1970s, and it went into regular use in 1982. Flying far enough inside friendly territory to avoid enemy anti-aircraft missiles, the AWACS radar has a range of between 200 km (for small aircraft or cruise missiles flying close to the ground) to 600 km (for large aircraft flying at high altitude). The AWACS tracks several hundred friendly and enemy aircraft at once. The AWACS acts as an airborne command center for aircraft. Friendly planes are kept out of each other's' way (there has not been a friendly air-to-air collusion since the 1991 Gulf war and the first major use of the E-3). Enemy aircraft are spotted, identified and friendly interceptors assigned to take care of the threat. One or more AWACS is used to control an air operation and each can stay up eleven hours at a time, or up to 22 hours with refueling and extra crew on board to man the equipment. The AWACS functions as a combination radar platform and command center.