Britain has insisted its airbases remain safe after the US military moved several aircraft from RAF Mildenhall, in eastern England.
It comes as US media report the evacuations were prompted by a threat from Iran.
Iran has denied any links to specific attacks in Britain, but its Revolutionary Guards have said airbases used by US forces there and in other countries are legitimate targets.
Britain has insisted its military bases remain safe after the US moved large refuelling aircraft from a UK airbase amid US media reports of a threat from Iran.
The removal of aircraft from RAF Mildenhall, first reported by the Wall Street Journal, marks the second such apparent evacuation in three months.
Commercially available flight tracking data showed at least 10 Boeing KC-135R Stratotanker refuelling planes left the base, in eastern England, on Monday, local time.
One flew to a base in Germany, one to Scotland and two to Spain, while the destinations of the other six were not reported.
At least three Osprey multipurpose aircraft also departed from Mildenhall and landed at Lakenheath, another RAF base four miles away.
Video filmed by a member of the public from outside the base and verified by Reuters showed two Ospreys taxiing on the runway after landing at Lakenheath.
