The aircraft, an RC-135U 'Combat Sent', intended to monitor enemy radar systems, was sighted on Tuesday morning flying above the Baltic states and looping around Kaliningrad, Russia’s exclave between Poland and Lithuania.

The U.S. jet left RAF Mildenhall at 7.32am and arrived back just over six hours later at 2.36pm.

The plane took off from RAF Mildenhall(Image: Newsquest)

According to the US Air Force, the RC-135U provides "strategic electronic reconnaissance information to the president, secretary of defence, Department of Defence leaders, and theatre........

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