AEW&C aircraft are used for both defensive and offensive air operations, and are to the NATO and US forces trained or integrated Air Forces what the Command Information Center is to a US Navy warship, plus a highly mobile and powerful radar platform. The system is used offensively to direct fighters to their target locations, and defensively, directing counterattacks on enemy forces, both air and ground. So useful is the advantage of command and control from a high altitude, the United States Navy operates Northrop Grumman E-2 Hawkeye AEW&C aircraft off its Supercarriers to augment and protect its carrier Command Information Centers (CICs). The designation airborne early warning (AEW) was used for earlier similar aircraft, such as the Fairey Gannet AEW.3 and Lockheed EC-121 Warning Star, and continues to be used by the RAF for its Sentry AEW1, while AEW&C (airborne early warning and control) emphasizes the command and control capabilities that may not be present on smaller or simpler radar picket aircraft. AWACS (Airborne Warning and Control System) is the name of the specific system installed in the E-3 and Japanese Boeing E-767 AEW&C airframes, but is often used as a general synonym for AEW&C.
Modern AEW&C systems can detect aircraft from up to 400 km (220 nmi) away, well out of range of most surface-to-air missiles. One AEW&C aircraft flying at 9,000 m (30,000 ft) can cover an area of 312,000 km2 (120,000 sq mi). Three such aircraft in overlapping orbits can cover the whole of Central Europe. AEW&C systems communicate with friendly aircraft, vectoring fighters towards bogeys, providing data on threats and targets, help extend their sensor range and make offensive aircraft more difficult to track, since they no longer need to keep their own radar active to detect threats.
After having developed Chain Home--the first ground-based early-warning radar detection system--in the 1930s, the British developed a radar set that could be carried on an aircraft for what they termed "Air Controlled Interception". The intention was to cover the North West approaches where German long range Focke-Wulf Fw 200 Condor aircraft were threatening shipping. A Vickers Wellington bomber (serial R1629) was fitted with a rotating antenna array. It was tested for use against aerial targets and then for possible use against German E boats. Another radar equipped Wellington with a different installation was used to direct Bristol Beaufighters toward Heinkel He 111s, which were air-launching V-1 flying bombs.
In February 1944, the U.S. Navy ordered the development of a radar system that could be carried aloft in an aircraft under Project Cadillac. A prototype system was built and flown in August on a modified TBM Avenger torpedo bomber. Tests proved successful, with the system being able to detect low flying formations at a range in excess of 100 miles (160 km). The U.S. Navy then ordered production of the TBM-3W, the first production AEW aircraft to enter service. TBM-3Ws fitted with the AN/APS-20 radar entered service in March 1945, with some 36–40 eventually being constructed.
The Lockheed WV and EC-121 Warning Star, which first flew in 1949 served widely with both the US Air Force and US Navy and provided the main AEW coverage for US forces during the Vietnam war. It was to remain operational until replaced with the E-3 AWACS, its intended successor. Developed roughly in parallel, N-class blimps were also used as AEW aircraft, filling in gaps in radar coverage for the continental US, their tremendous endurance of over 200 hours being a major asset in an AEW aircraft, although lighter than air operations were discontinued in 1962 following a crash.
In 1958, the Soviet Tupolev Design Bureau was also ordered to design an AEW aircraft. After determining that the projected radar instrumentation wouldn't fit in a Tupolev Tu-95 or a Tupolev Tu-116, the decision was made to use the more capacious Tupolev Tu-114 instead. This solved the problems with cooling and operator space that existed with the narrower Tu-95 and Tu-116 fuselage. To meet the flight range requirements, production examples were fitted with an air-to-air refueling probe. The resulting system, the Tupolev Tu-126, entered service in 1965 with the Soviet Air Forces and remained in service until replaced by the Beriev A-50 in 1984.
Many countries have developed their own AEW&C systems, although the Boeing E-3 Sentry and Northrop Grumman E-2 Hawkeye are the most common systems worldwide. The E-3 Sentry was built by the Boeing Defense and Space Group (now Boeing Defense, Space & Security) and was based on the Boeing 707-320 aircraft. Sixty-five E-3s were built and it is operated by the United States, NATO, the United Kingdom, France, and Saudi Arabia.