The bombers were redeployed to their home bases in the United States, according to a Pentagon official who was not authorised to discuss sensitive military movements and spoke Sunday on condition of anonymity.
Aviation watchers such as the Military Air Tracking Alliance have observed dozens of B-52 and B-1 bombers operating out of RAF Fairford since the opening days of the Iran war.
Observers noticed a host of B-1 bombers fly out of the base on Sunday.
The move comes as President Donald Trump weighs options for his war on Iran - including new strikes - despite his initial promises to Americans that the campaign would last a matter of weeks.
"We have decisions that I'll make about Iran. Iran's been decimated. So the only question is - it'll either be the easy way, or the hard way," Trump told reporters on Saturday as he left the White House for an election rally in Ohio.
A dual British-Iranian national was arrested in central London last week on suspicion of plotting a terrorist attack following a security incident at RAF Fairford in late September.
In total, six people have been taken into custody and then released on bail during the investigation.
British authorities have linked the incident to Tehran.
Iran has denied involvement, but it has previously said it considers any base used to attack its territory a legitimate target.
UK officials say proxies linked to Iran have been behind a string of arson and other attacks in Britain and other countries, many of them targeting the Jewish community and intended to sow fear.
They have previously warned that Tehran could expand its targets in the UK if conflicts in the Middle East continue.
RAF Fairford, 160km west of London, has been used by American bombers during decades of conflicts in the Middle East.
The US military still maintains a large presence in the Middle East.
On Thursday, a US official said the recently deployed USS Theodore Roosevelt aircraft carrier, as well as the USS Malkin Island amphibious readiness group - a group of ships that together carry more than 7000 sailors and 2000 Marines - are heading for the region.
The official said the move could result in three carriers in the region as early as the end of October.
