Which aircraft made the EC-121R Batcat obsolete in Vietnam?

During the Vietnam War, the US Air Force operated a highly specialized version of the Constellation: the EC-121R, known as Batcat. The 553rd Reconnaissance Wing operated up to 30 of these aircraft. Its role began to decline when, on October 1, 1970, the QU-22B reached full operational status, reducing the need for the EC-121. A few weeks later, on December 15, 1970, the unit was deactivated.

The unit was established on paper on February 9, 1967, and organized on February 25 of that year. From October 31, 1967, to December 15, 1970, it was based at Korat Royal Thai Air Force Base, from where its EC-121R aircraft flew missions over Southeast Asia. The choice of a four-engine piston aircraft derived from an airliner matched the need to stay airborne for many hours — a trait the Constellation family had amply demonstrated in its civilian career.

The EC-121R belonged to the EC-121 family, the electronic reconnaissance versions of the Constellation that the Navy and Air Force operated from 1954 onward. Known as the Warning Star, these aircraft were designed for early warning with large radomes above and below the fuselage, and over time also took on signals intelligence duties. In Vietnam, the QU-22B reaching full operational capability in October 1970 marked the beginning of the end for the Batcats: barely two and a half months later, the unit that operated them from Korat ceased to exist.