A British spy plane was monitored through a mobile phone app as it carried out surveillance on Russian air defences.
Plane spotters were able to watch the £650m Rivet Joint through Flightradar24.com or Planefinder as it flew near the Russian exclave of Kaliningrad, the Daily Mail reported.
They were able to monitor the aircraft’s speed, flight number and route as it flew off the coast.
Radar pictures shared on social media suggest the RAF aircraft, which was accompanied by US spy planes and F-35A stealth fighters, flew within 60 miles of the Russian base at a speed of 478 knots.
RAF RC-135W ZZ664 RRR7220 departed Waddington - Baltic mission pic.twitter.com/t2xaI5TACr— Mil Radar (@MIL_Radar) April 25, 2017
Justin Bronk, from the Royal United Services Institute think-tank, told the paper the plane would have been revealed by its transponders, which can only be turned off in a war zone.
“European airspace is extremely crowded so there is a limit to what it can do silently,” he said.
He said the aircraft would have been monitoring Russian air defences and taking readings of their search radars.
“The UK and US aircraft were most likely trying to provoke a response, because usually the Russians wouldn’t broadcast their highest end radar waveforms for Britain and the US to collect and analyse.”
It comes after revelations more Nato fighter jets have been scrambled to monitor and intercept Russian planes than at any time since the Cold War.