A contract to create EF-111s from existing F-111A airframes was awarded to Grumman in 1974. Flew on 10 March 1977, and deliveries to combat units began in 1981. The EF-111A Raven retained the F-111A's navigation systems, with a revised AN/APQ-160 radar primarily for ground mapping. The primary feature of the Raven, however, was the Raytheon AN/ALQ-99E jamming system, developed from the Navy's ALQ-99 on the Prowler. Its primary electronics were installed in the weapons bay, with transmitters fitted in a 16 feet (4.9 m) long ventral "canoe" radome; the complete installation weighed some 6,000 pounds (2,700 kg). Receivers were installed in a fin-tip pod, or "football", similar to that of the EA-6B. The aircraft's electrical and cooling systems had to be extensively upgraded to support this equipment. The cockpit was also rearranged, with all flight and navigation displays relocated to the pilot's side, and flight controls except throttles being removed from the other seat, where the electronic warfare officer's instrumentation and controls were installed.