RAF Typhoons have been scrambled in response to “unidentified aircraft” approaching UK airspace.
The fighter jets took off from RAF Lossiemouth on Monday carrying the latest Meteor air-to-air missile for the first time, the Ministry of Defence (MoD) said.
The “quick reaction alert” mission was undertaken as a “precautionary measure”, it added.
The MoD has not confirmed any further details about the unidentified aircraft.
The Meteor, which can fly in any weather, was developed by a six-nation European partnership led by the UK, creating 430 jobs across the country.
“The introduction of Meteor brings a new and innovative long-range capability and further enhances Typhoon’s already potent arsenal,” it added.
Defence Secretary Gavin Williamson said the missile would “provide an unrelenting deterrence to those who wish harm upon the UK and our armed forces”.
He added: “This latest missile system demonstrates the next chapter of the Typhoon which will see the jet evolve its ability to target and destroy any airborne threat at great distances.”