E-3A

E-3 Sentry
An E-3 Sentry of the United States Air Force
Role	Airborne early warning and control (AEW&C)
National origin	United States
Manufacturer	Boeing Defense, Space & Security Westinghouse Electric (radar)
First flight	EC-137D: 9 February 1972 E-3: 25 May 1976
Introduction	March 1977
Status	Operational
Primary users	United States Air Force NATO Royal Air Force Royal Saudi Air Force
Produced	1977–1992
Number built	68
Unit cost	US$270 million (FY1998 constant dollars)
Developed from	Boeing 707

The Boeing E-3 Sentry, commonly known as AWACS, is an American airborne early warning and control (AEW&C) aircraft developed by Boeing as the prime contractor. Derived from the Boeing 707, it provides all-weather surveillance, command, control, and communications, and is used by the United States Air Force, NATO, Royal Air Force, French Air Force, and Royal Saudi Air Force. The E-3 is distinguished by the distinctive rotating radar dome above the fuselage. Production ended in 1992 after 68 aircraft had been built.

In the mid-1960s, the US Air Force (USAF) was seeking an aircraft to replace its piston-engined Lockheed EC-121 Warning Star, which had been in service for over a decade. After issuing preliminary development contracts to three companies, the USAF picked Boeing to construct two airframes to test Westinghouse Electric and Hughes's competing radars. Both radars used pulse-Doppler technology, with Westinghouse's design emerging as the contract winner. Testing on the first production E-3 began in October 1975.

The first USAF E-3 was delivered in March 1977, and during the next seven years, a total of 34 aircraft were manufactured. NATO, as a single identity, also had 18 aircraft manufactured, basing them in Germany. The E-3 was also sold to the United Kingdom (seven) and France (four) and Saudi Arabia (five, plus eight E-3-derived tanker aircraft). In 1991, when the last aircraft had been delivered, E-3s participated in Operation Desert Storm, playing a crucial role of directing coalition aircraft against the enemy. Throughout the aircraft's service life, numerous upgrades were performed to enhance its capabilities. In 1996, Westinghouse Electric's Defense & Electronic Systems division, was acquired by Northrop Corporation before its being renamed Northrop Grumman Electronic Systems, which currently supports the E-3's radar.