What did the US Navy use four Constellations for in the Vietnam War?

The US Navy operated the Super Constellation as a transport under the designation R7V-1. The 18 examples it still had left were renamed C-121J when the armed forces' designations were unified, and several specialized versions were created from that base.

Four C-121Js were converted into television broadcast aircraft, designated NC-121J, for use in the Vietnam War. They were part of Project Jenny and were operated by VXN-8, known as the "Blue Eagles." The idea was to use a long-endurance aircraft, capable of staying airborne for hours, as a flying broadcast antenna over areas where no ground television network existed.

The C-121J also gave rise to other variants. Four were converted into VC-121Js for VIP transport, and one of them flew with the Blue Angels, the Navy's aerobatic team. Another example, the TC-121J, served as an electronic test bed.

The Air Force followed a parallel path with its radar aircraft: five EC-121Ds were modified as radio and television aircraft for psychological warfare operations, forerunners of the EC-130 Commando Solo, which would inherit that mission in the following decades.

These conversions show the versatility of an airframe conceived as a passenger aircraft: its wide, pressurized cabin and long range allowed broadcast equipment, radars, or VIP cabins to be installed without redesigning the aircraft.

In the same conflict, the Air Force's 553rd Reconnaissance Wing, activated in 1967 and based in Thailand, used EC-121R aircraft to monitor the Ho Chi Minh Trail in 8-hour shifts.