Photo copyright: Reuters
At least 10 US Air Force tanker aircraft left a second air base in the UK on Monday.
Flight tracking data seen by BBC Verify shows the planes took off from RAF Mildenhall in Suffolk and landed at other US bases in Europe and at Prestwick Airport in Ayrshire.
The Wall Street Journal writes that this was done in response to a threat from Iran, but the BBC has not yet been able to confirm this information from independent sources.
In October, the US withdrew its bombers from Fairford Air Force Base due to a security incident allegedly involving Iran.
A UK Ministry of Defense spokesman told the BBC: “We do not normally comment on the activities of other countries. Aircraft and other assets are regularly moved according to operational needs.”
The BBC has contacted the Pentagon for comment.
Using public tracking site Flightradar24, BBC data verification service BBC Verify was able to record that US Air Force KC-135 tanker aircraft were flying out of Mildenhall base throughout the day on Monday.
The first two planes headed to American bases in Germany and Italy. The first KC-135 then returned to Mildenhall before heading east and landing at Spangdahlem Air Base in Germany. Another plane flew to the Aviano airbase in Italy, made several circles over it and also went to Spangdahlem.
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Flight tracking data also shows eight more US KC-135 aircraft took off from Mildenhall later on Monday.
The plane that landed at Prestwick on Monday belongs to the Nebraska National Guard in the US, so it could have been a routine stop before returning to base.
Education Secretary Lucy Powell, responding on behalf of the Government to a question about the evacuation of US aircraft from Mildenhall base, told the BBC's BBC Breakfast programme: "I cannot comment on current operational matters, but please be assured that we take the security of our bases extremely seriously and will always act in accordance with operational intelligence when necessary."
A US Air Force spokesman said its aircraft "move between bases and deployments for a variety of reasons, including training and operational needs."
“U.S. military aircraft are deployed in accordance with access, basing and overflight agreements with our allies and partners. To ensure the security of operations, we will not provide additional information about the movement of military equipment,” the representative of the US military added.
Former UK national security adviser Lord Ricketts told the BBC: “We're talking about an airbase where these large tanker aircraft are based. Of course, these are large targets, and the airbase has a long perimeter, so it is inevitably vulnerable.”
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Reports of movements at Mildenhall base came after an incident at RAF Fairford, a US-run air base in Gloucestershire.
In September, three suspicious vans were spotted near the base. It later emerged that the US had withdrawn its bombers from the base and returned them to America.
In October, two British citizens appeared in court in connection with an alleged plot linked to Iran. Eight people have been arrested as part of an investigation by anti-terrorism police.
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