In December 1986, with no signs of improvement in the Nimrod AEW3 radar trials, the entire programme was finally cancelled, leaving 8 Squadron to carry on with its six remaining Shackletons. The U.K Government finally announced the aircraft's successor in 1988 in the form of the Boeing E-3D, or Sentry AEW1 as it would be known to the RAF. On the 5th Jan 1990 - The first Boeing E-3D Sentry AEW1 for the RAF, ZH101, made its first flight from the Boeing facility at Seattle. The AWACS aircraft was intended to replace the 'stop-gap' Shackleton AEW Mk 2 in service with No 8 Squadron.

The RAF operates seven E-3D Sentry aircraft in the airborne surveillance and command-and-control role. The aircraft are based at RAF Waddington, where they are operated by Nos 8 and 23 Squadrons as the UK’s contribution to the NATO Airborne Early Warning and Control Force. The E-3D also forms one arm of the UK Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR) triad of Sentinel R1, E-3D and Nimrod R1 aircraft. Whilst primarily procured as an airborne early warning aircraft, the E- 3D has been extensively employed in the Airborne Warning and Control System (AWACS) role.

The normal crew complement of 18 comprises four flight-deck crew, three technicians and an 11-man mission crew. The mission crew comprises a tactical director (mission crew commander), a fighter allocator, three weapons controllers, a surveillance controller, two surveillance operators, a data-link manager, a communications operator and an electronic-support- measures operator. The Sentry’s roles include air and sea surveillance, airborne command and control, weapons control and it can also operate as an extensive communications platform.

The aircraft cruises at 30,000ft and 400kts and its Northrop Grumman AN/APY-2 high-performance, multimode lookdown radar, housed in the black radome, is able to separate airborne and maritime targets from ground and sea clutter. One E-3D flying at 30,000ft can scan at distances of over 300nmls; it can detect low-flying targets or maritime surface contacts within 215nmls and it can detect medium-level airborne targets at ranges in excess of 280nmls. The multi-mode radar provides lookdown surveillance to the radar horizon and an electronic vertical scan of the radar beam provides target elevation and beyond-the-horizon operation for long-range surveillance of medium and high-altitude aircraft. These attributes allow it to determine the location, altitude, course and speed of large numbers of airborne targets. The aircraft’s mission systems can separate, manage and display targets individually on situation displays within the aircraft, or it can transmit the information to ground-based and ship-based units using a wide variety of digital data links.