NATO Air Base Geilenkirchen (E-3A Component) ( ICAO: ETNG) is located near Geilenkirchen, North Rhine-Westphalia, Germany. It is the main operating base of the NATO Boeing E-3 Sentry Component, one of two operational elements of the NATO Airborne Early Warning & Control Force. 

Following NATO's decision to establish the NATO Airborne Early Warning & Control Force program and to make the base near Teveren the Main Operating Base (MOB) of the E-3A Component, a major construction program was started in 1980 to modify the operational and support facilities. In January 1980 the first E-3A Component personnel started arriving at the base, and in October 1980 the NATO Defense Planning Committee (DPC) granted the E-3A Component the status of a NATO International Military Headquarters. E-3A Component flying operations began in February 1982 after delivery of the first E-3A aircraft. Germany formally handed over the main operating base to NATO on 31 March 1982. The component was officially activated on 28 June 1982 and reached full operational capability by the end of 1988.

The component operates fourteen (out of an original order for 18) Boeing E-3A AWACS aircraft all of which are based on the Boeing 707 airframe (the component also operated three (3) Boeing 707 Trainer Cargo Aircraft, but these have been retired since 2011). These 14 aircraft of the NATO E-3A Component are all registered in Luxembourg as part of that country's contribution to the NATO AWACS programme. Since coming into service in the early 1980s, the aircraft and their onboard systems and associated ground-based equipment have undergone regular upgrading. Normally, only a certain number of the E-3As are present at NATO Air Base Geilenkirchen at any given time. The remainder are deployed to the component's forward operating bases in Greece, Italy, Turkey, and the forward operating location in Norway, or to locations elsewhere. Each of these forward operating facilities is located on a national airbase.