Lincoln Shoot Down
Returning to the Lincoln incident this is mentioned in Spyflights of the Cold War by Paul Lashmar - 1998 from which I quote -
"..The Russians claimed that it penetrated 125km into their airspace. Documents in the Public Record Office released 30 years later confirm this.... The aircraft appears to have strayed completely off course..How the aircraft strayed remains an open question. The captain was a highly experienced pilot who had flown many bomber missions over Germany in the war.....It remains possible that while these were not ELINT aircraft that they (this and the earlier Lincoln flight) had a secret brief to provoke Soviet defences which were recorded from the ground. But as yet there is no evidence..."