The 7405th Support Squadron (SUPRON), a part of the 7499th Support Group mentioned earlier, based at Wiesbaden Air Base, Germany, until 1975,and later at Rhein-Main Air Base, flew the most successful covert Air Force reconnaissance mission of the Cold War. Beginning in about 1952, the 7405th SUPRON daily patrolled the twenty-mile-wide air Berlin Air Corridors leading from West Germany to Berlin and the forty miles in diameter control zone surrounding the city (Project Rain Drop). Technically, there was no need to resort to covertly configured aircraft because the four-power agreement governing the use of the air Berlin Air Corridors, drafted jointly by the Soviet Union, the United States, Great Britain, and France, did not prohibit any specific types of aircraft from using that airspace. Moscow's interpretation, however, was that the three western allies enjoyed aerial access to Berlin only to logistically support their military garrisons stationed there. Rather than make an issue of it, the United States elected to use cargo aircraft outfitted with covertly mounted sensors.
Over the years, the 7405 SUPRON's covert aircraft -- RB-47s, RB-29s, RC-97s, RC-130s, etc. -- collected optical imagery using a variety of cameras with focal lengths ranging from 6 inches for vertical photography to 240 inches for long-range oblique photography, as well as thermal imagery from vertical and forward-looking infrared systems. In addition, one of the RC-97s and one of the later RC-130s had electronic intercept suites. Sliding external panels covered the camera ports and all antennas, and dielectric domes were fully retractable. Still, for any number of reasons, the Soviets and East Germans knew perfectly well what was going on. Of all the aircraft transiting the Berlin Air Corridors, only those of the 7405th SUPRON requested their own navigation, followed routes different from other aircraft, routinely flew 500 feet off their assigned altitudes, and traced random flight patterns while in the Berlin Control Zone. Berlin Air Traffic Control Center, the American-operated radar facility that monitored and directed air traffic in the Berlin Air Corridors and control zone, allowed this freedom of action because it was privy to the mission. Further, the spectacle of transport aircraft landing at Berlin Tempelhof Airfield, and the crew (sometimes numbering upward of fifteen) having lunch and then returning to West Germany, with no effort to either onload or offload passengers or cargo, strained the cover story beyond any credibility. Moreover, ground-based photography taken through telephoto lenses clearly showed open camera doors up to 10,000 feet, the highest altitude allowed in the Berlin Air Corridors and control zone. Why did the Soviets, who had a veto on any aircraft entering the Berlin Air Corridors, allow the mission to operate even though it was hidden by only the barest of fig leaves? There is no way of knowing for certain, but several reasons suggest themselves. Supposedly covert flights spared the Soviets the insult of an overt reconnaissance mission operating in airspace over which they had control. East Germany, not the Soviet Union, was under observation, which understandably lessened nationalistic sensitivities. The Kremlin must have known that the United States would not pass up the chance to conduct aerial reconnaissance over the most heavily militarized section of the Warsaw Pact. Having positively identified the mission aircraft, they could, to a degree, control what was and was not seen. There was also tacit reciprocity, an unspoken understanding that by allowing the 7405th SUPRON to operate without interference, the Soviets could carry out similar missions using covertly configured aircraft, mainly civilian airliners, to venture into the West. Finally, there was probably an understanding by Moscow that allowing Berlin Air Corridor reconnaissance was a signal that it had nothing to hide, whereas denying that right would alert the West and raise tensions. Whatever the reasoning, the 7405th SUPRON's covert missions flew for almost four decades without a serious incident, giving the Berlin Air Corridor missions the advantage of being a low-risk endeavor that returned intelligence of great value. Although neither the Berlin air corridor missions nor the Air Force over-flights of the Soviet Union in the 1950s resulted in any losses to hostile action, other missions and aircraft were not so fortunate. Trouble with Moscow over peripheral reconnaissance began in 1947 when an RB-29 flew perilously close to the shoreline of the Chukotski Peninsula. Fortunately, the incident was resolved via diplomatic exchanges; unfortunately, that civility did not long endure. Beginning in 1950 and continuing on through the 1960s, the Cold War was littered with incidents involving hostile action taken against reconnaissance aircraft.
Those incidents illustrated the delicate balance inherent in peacetime reconnaissance and the potential consequences should either side upset that balance. With the exception of the U-2 missions that policed the cease-fire that ended the 1973 Middle East War, the United States never negotiated with any target nation the ground rules governing peacetime reconnaissance. Instead, the ground rules evolved through a process known as mission assessment, performed at various levels within the military and federal government. The assessment took into account a target nation's sensitivity to intelligence operations in general, the state of its relations with the United States, its shoot-down capability, and whether it flew reconnaissance missions of its own (tacit reciprocity). In all cases, whether or not an aircraft flew a particular route on a particular day was a judgment call that balanced the anticipated intelligence gain against the potential threat to the aircraft and its crew. No aircraft ventured into a high-threat area without the potential of gathering intelligence of great importance. In the vast majority of the cases, mission assessment proved valid, but the capriciousness of the Sino-Soviet bloc reactions, which sometimes seemed to border on the mindless, made it less than foolproof. Peacetime reconnaissance, therefore, despite the precautions, remained one of the more hazardous missions of the Cold War. Fighters intercepted American reconnaissance aircraft on numerous occasions and attacked them at least thirty-three times, resulting in the loss of eleven aircraft. Surface-to-air missiles destroyed two U-2s, and although it cannot be proven, three other aircraft disappeared under circumstances that suggest that they fell victim to hostile action. Three of the downed aircraft -- the U-2 of Francis Gary Powers (1960), an RC-130 over Soviet Armenia (1958), and a U-2 over Cuba (1962) -- had violated international boundaries, but as far as is known the other lost aircraft were operating in international airspace, well clear of any reasonable claims of sovereignty.
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