In the late 1960s and early 1970s, the Air Force was shopping around for possible replacements for its Douglas EB-66 ELECTRONIC WARFARE AIRCRAFT. Although the EB-66 still continued to fly combat missions over North Vietnam, it was rapidly beginning to show signs of age.
The Air Force rejected the development of a completely new type of aircraft for this role as being economically impractical because of the small number of aircraft required. At one time, some thought had been given to acquiring the Grumman EA-6B Prowler carrier-based electronic warfare aircraft, but the Air Force was reluctant to acquire yet another originally developed for the Navy. After some thought, the Air Force concluded ini 1972 that the modification of some existing F-111A strike fighters would be the most cost-effective solution.
However, the EA-6B was a four-seat aircraft, and it was concluded that it was impractical to adapt the F-111A to a four-seat configuration because it would reduce internal capacity too much. The only alternate was to develop equipment similar to the Tactical Jamming System of the EA-6B, but capable of being operated by a single electronics warfare officer.
In December 1974, the Grumman Aircraft Corporation of Calverton, Long Island was selected as the prime contractor for this conversion. On January 30, 1975, Grumman was awarded a contract for the modification of two F-111As (serials 66-0041 and 66-0049) as EF-111A prototypes, the E prefix standing for “Electronics”
Deadly Military Weapons 