The men, aged between 23 and 25, are British citizens from London. They were arrested early Sunday near RAF Fairford in Gloucestershire after police received reports of suspicious vehicles travelling towards the base.
Police said the suspects were initially detained under the Explosives Act and on suspicion of preparing a terrorist act. Counter Terrorism Policing is leading the investigation, while specialist teams continue examining the area.
Three vans were found near the base, with bomb disposal experts and other security teams deployed. A large area was placed under a security cordon, and more than 80 homes were evacuated as police investigated the incident.
A local farmer alerted police after seeing several vehicles and a group of masked and hooded men near the village. She said she became concerned because of the proximity of the activity to RAF Fairford and called emergency services.
UK authorities have not confirmed who may have been behind the suspected plot or what the suspects were allegedly planning to do.
Police are also examining whether the incident could have involved people acting for a foreign state. Iran has denied any involvement in the case.
RAF Fairford is an important military facility and has been used by the US military as a forward operating location. Its role in US military operations has made it a sensitive site amid rising tensions involving Iran.
Counter-terrorism investigators said the case remains active and that several new lines of inquiry have emerged. Authorities have asked the public to remain patient while the investigation continues.
