Conflicting accounts from a bystander who called the police and from President Trump have led to questions about whether security services knew about the possible plot in advance.
ยฉ Toby Shepheard/Reuters
Armed police officers stand guard on a road outside the perimeter of R.A.F. Fairford air base in southern England, on Monday.
The British counterterrorism police say the men were arrested after three suspicious vehicles appeared to be traveling toward R.A.F. Fairford early on Sunday.