At least 10 US Air Force refuelling aircraft left a second airbase in Britain on Monday. Flight tracking data seen by BBC Verify shows the aircraft left RAF Mildenhall in Suffolk and landed at other American bases in Europe and also at Prestwick Airport in Ayrshire. The Wall Street Journal reported that this was in response to a threat from Iran but the BBC has not independently verified that claim. Monday's departures come weeks after the US withdrew its bombers from RAF Fairford airbase over a suspected Iran-linked security incident. Asked about Monday's flights, an MoD spokesperson told the BBC: "We do not routinely comment on the activity of other nations. Aircraft and other assets move regularly according to operational requirements." Using public tracking site Flightradar24 BBC Verify has been able to see USAF KC-135 tankers leaving Mildenhall throughout Monday.