USSR spies used civilian airlines

The Soviet Union used civil airliners to conduct secret Cold War spying missions over Britain, according to newly published Government files.

Some aircraft would switch off their transponders, alerting air traffic controllers to their position before veering off their approved flight paths to carry out aerial intelligence-gathering missions over sensitive targets, papers released by the National Archives under the 30-year rule show.

In a memorandum marked Secret for UK US Eyes Only, Defence Secretary John Nott informed prime minister Margaret Thatcher in December 1981 that the RAF was monitoring the hundreds of monthly flights through UK airspace by Warsaw Pact airliners.