The E-3 Sentry's airframe is a modified Boeing 707-320B Advanced model. USAF and NATO E-3s have an unrefueled range of some 4,000 mi (6,400 km) or eight hours of flying. The newer E-3 versions bought by France, Saudi Arabia and the UK are equipped with newer CFM56-2 turbofan engines, and these can fly for about 11 hours or about 5,000 mi (8,000 km). The Sentry's range and on-station time can be increased through air-to-air refueling and the crews can work in shifts by the use of an on-board crew rest and meals area.

When deployed, the E-3 monitors an assigned area of the battlefield and provides information for commanders of air operations to gain and maintain control of the battle; whilst as an air defense asset, E-3s can detect, identify and track airborne enemy forces far from the boundaries of the U.S. or NATO countries and can direct fighter-interceptor aircraft to these targets. In support of air-to-ground operations, the E-3 can provide direct information needed for interdiction, reconnaissance, airlift and close-air support for friendly ground forces.

The unpressurized dome is 30 feet (9.1 m) in diameter, six feet (1.8 m) thick at the center, and is held 11 feet (3.4 m) above the fuselage by two struts. It is tilted down 6° at the front to reduce its air drag during take-offs, and while flying endurance speed (which is corrected electronically by both the radar and SSR antenna phase shifters). The dome uses both bleed-air and cooling doors to remove the heat generated by electronic and mechanical equipment. The hydraulically-rotated antenna system permits the Westinghouse Corporation's AN/APY-1 and AN/APY-2 passive electronically scanned array radar system to provide surveillance from the Earth's surface up into the stratosphere, over land or water.

Other major subsystems in the E-3 Sentry are navigation, communications, and computers. Consoles display computer-processed data in graphic and tabular format on video screens. Console operators perform surveillance, identification, weapons control, battle management and communications functions. The radar and computer subsystems on the E-3 can gather and present broad and detailed battlefield information. This includes position and tracking information on enemy aircraft and ships, and location and status of friendly aircraft and naval vessels. The information can be sent to major command and control centers in rear areas or aboard ships. In times of crisis, data can be forwarded to the National Command Authority in the U.S. via RC-135 or naval aircraft carrier task forces.

Electrical generators mounted on each of the E-3's four engines provide one megawatt of electrical power that is required by the E-3's radars and other electronics. Its pulse-Doppler radar has a range of more than 250 mi (400 km) for low-flying targets at its operating altitude, and the pulse "beyond the horizon" radar has a range of approximately 400 mi (650 km) for aircraft flying at medium to high altitudes. The radar combined with a secondary surveillance radar to provide a look down to detect, identify and track enemy and friendly low-flying aircraft while eliminating ground clutter returns.

This is the one instance where you can go inside the aircraft and not photograph anything inside due to the sensitivity of the equipment.