Which Navy aircraft gave rise to the B-66 Destroyer?

The Douglas B-66 Destroyer was developed for the USAF as a derivative of the US Navy's A-3 Skywarrior, a heavy carrier-based attack aircraft. The official intent was for it to be a simple development of the A-3, exploiting its strictly land-based role to do away with unnecessary naval features.

The USAF's requirements proved extensive and widely divergent, forcing considerable changes to the design. Both the fuselage and the wing were redesigned from scratch, rather than simply stripping out the naval features. The supposedly simple conversion ended up being, in essence, an entirely new aircraft. The A-3 carried two Pratt & Whitney J57 turbojets, while the B-66 mounted two Allison J71s. One significant difference was equipping the B-66 with ejection seats, which the A-3 lacked entirely. The B-66 is cited as a classic example of aircraft conceived, to save money, as a mere modified version of an existing type.

Conceived as a light bomber, the B-66 never dropped a bomb in combat, but it had a solid service record as an electronic warfare aircraft during the Vietnam War. The unarmed EB-66B, EB-66C and EB-66E flew numerous missions in that conflict. They gathered electronic intelligence on North Vietnamese defenses and protected bombing missions by Republic F-105 Thunderchiefs by jamming North Vietnamese radars. They routinely operated as support aircraft for other aircraft operating over North Vietnam and Laos. The platform also served as an airborne command post for USAF strikes, controlling mainly F-105 Thunderchiefs.