Lockheed Constellation EC-121M

The US Navy ordered 142 airborne early warning Constellations based on the L-1049 Super Constellation, designated PO-2W, with deliveries from 1953; in 1954 they became the WV-2. From that fleet came a branch quite unlike the rest: thirteen aircraft were turned into the WV-2Q, dedicated to electronic intelligence (ELINT), that is, detecting and recording the emissions of other nations' radars and communications systems. When aircraft designations were standardised across the Department of Defense in 1962, the WV-2 became the EC-121K and the WV-2Q the EC-121M.

The aircraft kept the four-engined airframe and the great endurance of the Super Constellation, qualities meant for long radar patrols that proved just as useful for loitering for hours off a hostile coast, always in international airspace, while operators and linguists listened to what was happening on the other side.

The EC-121M served with two Fleet Air Reconnaissance Squadrons. VQ-1 flew from Naval Air Facility Atsugi in Japan; VQ-2 operated from Naval Station Rota in Spain. Both kept the eavesdropping Constellation in service until it was replaced by the EP-3B Orion and EP-3E Aries.

In the late 1960s these Pacific missions went by the code name "Beggar Shadow": a Navy programme to gather intelligence on the Soviet Bloc nations and their communications without leaving international airspace. Although nominally under the Seventh Fleet and the Pacific command, they were controlled operationally by the Naval Security Group detachment at Kamiseya, Japan, under the direction of the National Security Agency. In the first three months of 1969 alone, nearly 200 similar Navy and Air Force missions had been flown off North Korea's east coast without incident.

The EC-121M designation was also carried by one unusual Air Force aircraft. In August 1967 a modified EC-121K, later redesignated EC-121M and known as Rivet Top, began operational testing in Thailand. Besides interrogators able to read two additional Soviet transponders, it carried the top-secret Rivet Gym installation: Vietnamese-speaking intelligence specialists at four voice intercept stations who could hear the conversations between MiGs and their ground controllers. Its limitations were serious - without radar scopes the operators could not tell which American aircraft was under threat, and the secrecy surrounding the source undermined the credibility of its warnings - yet its value kept it at Korat until 1969, and by the end of May 1968 the Rivet Gym equipment had been back-fitted to every College Eye EC-121.

At 07:00 on Tuesday 15 April 1969 an EC-121M of VQ-1 took off from Atsugi: Navy Bureau number 135749, tail code "PR-21", radio call sign "Deep Sea 129". On board were 8 officers and 23 enlisted men under Lieutenant Commander James Overstreet; nine of them, including one Marine NCO, were cryptologic technicians and linguists in Russian and Korean. The task was a routine signals intelligence collection flight: cross the Sea of Japan to the area off Musu Point, fly an elliptical racetrack orbit some 222 km long there, and then land at Osan in South Korea. Orders forbade it from coming closer than about 90 km to the North Korean coast; VQ-1 had flown the route for two years and the mission was graded "minimal risk".

At 12:34, some six hours into the flight, radars detected two North Korean MiG-21s taking off near Wonsan. At 13:00 the aircraft sent its scheduled activity report with nothing unusual: it was its last message. At 13:44 VQ-1 radioed a warning of possible attack; Overstreet acknowledged it and turned to abort, but the supersonic MiGs, armed with cannon and missiles, easily overtook the unarmed, unescorted Constellation. At 13:47 the radar tracks merged, and two minutes later the EC-121M vanished from the screens. It came down some 167 km off the coast and all 31 crew, 30 sailors and one Marine, were killed: the largest single loss of US aircrew of the Cold War. (One accident listing credits the shootdown to MiG-17s; the dedicated account of the incident names MiG-21s.)

North Korean media claimed the aircraft had intruded deep into its airspace and had been downed "with a single shot". The Soviet Union, at the height of the Cold War, sent two destroyers to help with the recovery. Washington weighed retaliation options that even included nuclear weapons, but the Nixon administration settled for assembling Task Force 71, with several carriers and the battleship New Jersey, one of the largest shows of force in the region since the Korean War. Kissinger later described that response as weak, indecisive and disorganised. Nixon ordered reconnaissance flights resumed within a week, to show that the United States would not be intimidated while avoiding a confrontation.

The EC-121M went on listening from Atsugi and Rota until the EP-3s arrived. Besides Deep Sea 129, three other aircraft of the type were lost in accidents, among the 20 Navy EC-121s destroyed in that way.