The United States probed the coastal defenses of the Soviet Union with thousands of "Ferret" spy flights during the Cold War and at least 31 flights were shot down, according to a published report.
At least 138 American pilots and crewmen who flew the highly secret espionage flights in the 1950s and 1960s remain unaccounted for, according to data developed by U.S. News and World Report and the ABC news program, "Primetime Live."Citing U.S. declassified government records, the two news organizations said that at least 252 American airmen were shot down while flying espionage or support missions between 1950 and 1970.
According to the U.S. News report, 24 are known to have been killed while 90 are known to have survived.
The official cover story at the time was that any planes flying near Soviet borders were engaged in "electromagnetic research" or "photographic mapping missions," U.S. News said.
The U.S. government publicly has admitted to one violation of Soviet air space: the 1960 U-2 flight of Francis Gary Powers, in which the airman was shot down, creating an international incident that strained ties between the two super-powers.
The news magazine also said that the large number of airmen unaccounted for indicates that some must have been captured and imprisoned.
Next month, a U.S. task force will be in Russia to ask authorities about the whereabouts of the missing airmen, the report said.
The report, based on recently declassified documents, found that there were as many as 1,000 espionage flights over the Soviet Union in the 1950s, with the figure nearly tripling in the next decade.
The spy missions were considered so sensitive that hours after the November 1963 assassination of President John F. Kennedy in Dallas the Air Force and the CIA urgently recalled the "Ferret" espionage planes then in Soviet air space to avoid provoking Moscow, the report said.
U.S. airmen who flew the spy planes knew they were expendable, the news report said.
To maintain secrecy, search-and-rescue planes ordered to retrieve downed U.S. crews were at times dispatched to areas far from the regions where the missions actually were flown, it said.