RAF jets intercepted two Russian bombers as they approached the UK on Wednesday.
The incident off north-east Scotland came during the closing stages of a major military exercise involving the Royal Navy's new aircraft carrier.
Two new Poseidon maritime patrol aircraft also arrived at RAF Lossiemouth in Moray on Wednesday.
The quick reaction alert (QRA) incident involved Typhoon jets flown from Leuchars in Fife.
The jets and crews are usually stationed at Lossiemouth but were temporarily moved to Leuchars during a £75m revamp of the Moray station's runways.
Working with the Norwegian air force, the RAF crews "shadowed" the two Tu-160 Blackjack bombers until they left the "UK's area of interest", the RAF said.
A Voyager fuel tanker aircraft from RAF Brize Norton in Oxfordshire also joined the mission to refuel the Typhoons.
The Typhoons involved in the QRA flew to Lossiemouth after the completion of the mission.
QRAs have happened since the Cold War era of the late 1940s to early 1990s.
The RAF say the Russian aircraft pose a risk to civilian flights because of their lack of communication with air traffic control.
Some of the Russian aircraft also trail five-mile (8km) long wire antenna behind them, which the RAF say also poses a risk to civilian traffic.
Wednesday's QRA came amid military activity around north-east Scotland.
Exercise Joint Warrior, UK-led Nato training involving new Royal Navy carrier HMS Queen Elizabeth, was being wound down.
Over the past two weeks the exercise had seen live firing by jets at ranges in the Highlands and simulated aerial attacks on HMS Queen Elizabeth involving more than 20 aircraft.