Two unidentified drones have reportedly come perilously close to RAF jets in British skies.
One was reportedly spotted hovering at about 17,000 ft - 40 times above the legal limit for commercial drones, according to The Telegraph.
The near misses happened days apart over the North Sea in February this year.
The RAF was conducting simulated air combat training and an air-to-air refuelling exercise, it is reported.
Incident logs seen by The Telegraph show the air force flagged the sightings with police and "multiple different external investigations" were launched.
The source of the drones has not been revealed.
An RAF Typhoon fighter jet
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Defence experts have warned of drones spotted over US air bases in Norfolk and Suffolk were linked to a Russian ship just off the coast.
The first near-miss happened on February 18, when an RAF Airbus Voyager tanker was refuelling a Typhoon fighter jet off Cromer in Norfolk.
Incident logs reported that the unidentified object came so close to the tanker that its pilot instinctively ducked.
The second incident happened on February 23. A Typhoon was practising dogfights with another jet when its pilot reportedly spotted a “black circular object pass directly above him”.
Commercial drones are usually subject to a 400ft flying ceiling to minimise the risk of interference with other aircraft.
However a spokesperson said they "remain highly vigilant to the potential threats posed to defence and stand ready to respond appropriately".
They added: "While reports of drones sightings are not necessarily hostile, where activity is assessed to pose a credible threat, Defence has measures available to respond appropriately and we do not comment on specific threat assessments."