The E-3 Sentry is a modified Boeing 707 commercial airframe with a rotating radar dome. Its mission is to be an airborne warning and control system, or AWACS.Fact Sheets:http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104504/e-3-sentry-awacs.aspxhttp://www.boeing.com/boeing/history/boeing/airborne.