The Boeing E-3 sentry is a military airborne warning and control system (AWACS) aircraft that provides all-weather surveillance, command, control and communications to the United States, United Kingdom, France, NATO and other air defense forces. The E-3 offers superior surveillance capabilities. The E-3 Sentry is a modified Boeing 707-320B Advanced Commercial Airframe. It is a militarized version of the Boeing 707-320B commercial jetliner airframe.

The USAF E-3 fleet completed its largest upgrade which is the Block 30/35 Modification in 2001. The four enhancements were the Electronic Support Measures (ESM) for passive detection, Joint Tactical Information Distribution System (JTIDS) to provide secure, anti-jam communication, memory capability enhancement in the computer and Global Positoning System (GPS).

E-3 Sentry aircraft were among the first to deploy during Operation Shield where they immediately established an around-the-clock radar screen to defend against Iraqi forces. In its strategic defense role, the E-3 provides the means to detect, identify, track and intercept airborne threats.

The E-10 MC2A, based upon the Boeing 767-400ER airframe, was intended to replace the United States operated E-3 (along with the RC-135 and the E-8 Oint STARS), but budget cutbacks have clouded its future.

Production ended in 1992 after 68 had been built.