Police did not detect explosives in vans found near Royal Air Force Fairford, adding uncertainty around a suspected terrorism plot.
Police provided no further details on the latest suspect beyond identifying him as a 27-year-old man who was detained in London.
There have been nearly 4,000 deaths and more than 8,000 cases in the fast-growing outbreak.
Authorities were trying to determine how an Omani co-pilot nearly crashed a Tel Aviv-bound jet. An Israel official said the co-pilot had “the motive to kill Jews."