Since entering service in 1964 the E-2 has protected US Navy carrier battle groups and acted as an airborne controller for their aircraft. One of very few types designed specifically for the airborne early warning (AEW) role, it was first flown in prototype form as long ago as October 1960. As a consequence of its ability to operate from aircraft carriers, the basic Hawkeye is extremely compact.
A total of 59 production E-2As was delivered from January 1964; 51 were updated to E-2B standard, before production switched to the improved E-2C. The first E-2C flew on 23 September 1972 and Grumman built 139 for the US Navy when the line closed in 1994. However, low-rate production began again in 2000.
External changes to the E-2 have been minor but its systems have been progressively updated. The E-2C was initially equipped with APS-125 search radar, but this was replaced by the AN/APS-139 in Group I aircraft from 1988 and the AN/APS-145 in the latest Group II E-2Cs. The latter radar allows a low-flying, fighter-sized aircraft to be detected at up to 253 miles (407 km) away with the E-2C flying at its operational altitude. A passive detection system gives warning of hostile emitters at ranges up to twice the radar detection range.
For over 30 years in service, the E-2C is still an evolving design, and Northrop Grumman is developing the even more capable E-2C Group II Plus or Hawkeye 2000; new-build aircraft were scheduled to enter US Navy service in late 2001. The E-2 currently equips 14 US Navy squadrons and is destined to remain in service until as least 2020. E-2Cs have been exported to Egypt (6), France (2), Israel (four, currently in storage), Japan (13), Singapore (4) and Taiwan (4). Many customers are upgrading their E-2s to a mix of Group II or Hawkeye 2000 standards.