The then Prime Minister Pandit Jawaharlal Nehru approved overflight by U-2 missions covering the border areas with China on November 11, 1962, the independent National Security Archive (NSA) said in a report based on the latest set of declassified documents it obtained from the CIA under the Freedom of Information Act.
The use of Charbatia, an abandoned World War II base in Orissa, was agreed during a meeting between the then US President John F Kennedy and Indian President S Radhakrishnan on June 3, 1963, but Indian work to improve it took longer than expected, so the missions resumed from Thailand's Takhli, NSA said, based on the 400-page CIA report released by it.
In fact, the longest U-2 mission to date was the one flown from Takhli on September 29, 1963, it said.
NSA said that the first deployment to Charbatia in May 1964 ended because Nehru died.
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According to a newly declassified CIA history of the U-2 programme obtained under the Freedom of Information Act by National Security Archive, it was the secret flights made by these U-2s aircrafts by the CIA, which informed India about the nature of Chinese incursions inside Indian territory.
"The pilots and aircraft left Charbatia but other remained in place to save staging costs. In December 1964, when Sino-Indian tensions increased along the border, Detachment G returned to Charbatia and conducted three highly successful missions, satisfying all of COMOR's requirements for the Sino-Indian border region," it said.
"By this time, however, Takhli had become the main base for Detachment G's Asian operations, and Charbatia served merely as a forward staging base. Charbatia was closed out in July 1967," the report said.