During the Vietnam War some 40 EC-121s were modified from USN WV-2 and WV-3 early warning Constellations for use with ground sensors to detect enemy troop movements along the Ho Chi Minh Trail and 25 were deployed to Korat RTAFB as a part of Operation Igloo White.
 The resulting EC-121R configuration was nicknamed the Batcat.
2 Batcats were lost during the war, with the loss of 22 crewmen, one in a takeoff accident during a thunderstorm in April 1969, the other in September 1969, in a landing accident.
4 Thai civilians were also killed in the second crash.

Batcat EC-121s were camouflaged in standard 3-color Southeast Asia scheme while the College Eye/Disco early warning aircraft were not.
BatCat missions were 18 hours in length, with 8 hours on station at one of 11 color-coded orbits used during their 5-year history, 3 of which were over South Vietnam, 6 over Laos, 1 over Cambodia and 1 over the Gulf of Tonkin.

EC-121Rs were operated by the 553d and 554th Reconnaissance Squadrons of the 553d Reconnaissance Wing, between October 1967 and December 1970, with appx.
20 Batcats on hand at any time.
The Wing in
activated in December 1970 and the 554th RS relocated to Nakhon Phanom RTAFB to fly QU-22 sensor monitors nicknamed "Baby Bats".
Initially with 11 aircraft, the 553rd RS continued ops for another year, gradually returning aircraft and crews to the USA.
The final Batcat mission was in December 1971.
The last remaining administrative and support personnel returned to Otis AFB in January 1972.
During the Vietnam War some 40 EC-121s were modified from USN WV-2 and WV-3 early warning Constellations for use with ground sensors to detect enemy troop movements along the Ho Chi Minh Trail and 25 were deployed to Korat RTAFB as a part of Operation Igloo White.  The resulting EC-121R configuration was nicknamed the Batcat. 2 Batcats were lost during the war, with the loss of 22 crewmen, one in a takeoff accident during a thunderstorm in April 1969, the other in September 1969, in a landing accident. 4 Thai civilians were also killed in the second crash.
Batcat EC-121s were camouflaged in standard 3-color Southeast Asia scheme while the College Eye/Disco early warning aircraft were not. BatCat missions were 18 hours in length, with 8 hours on station at one of 11 color-coded orbits used during their 5-year history, 3 of which were over South Vietnam, 6 over Laos, 1 over Cambodia and 1 over the Gulf of Tonkin.
EC-121Rs were operated by the 553d and 554th Reconnaissance Squadrons of the 553d Reconnaissance Wing, between October 1967 and December 1970, with appx. 20 Batcats on hand at any time. The Wing in
activated in December 1970 and the 554th RS relocated to Nakhon Phanom RTAFB to fly QU-22 sensor monitors nicknamed "Baby Bats". Initially with 11 aircraft, the 553rd RS continued ops for another year, gradually returning aircraft and crews to the USA. The final Batcat mission was in December 1971. The last remaining administrative and support personnel returned to Otis AFB in January 1972.
Lockheed EC-121 Warning Star