The Air Force didn’t identify who was behind the incursions, but said officials determined there was no impact on residents or critical infrastructure.

A comprehensive look at how the situation, which an anonymous U.S. official said appears to be coordinated and not the work of hobbyists, has unfolded so

LONDON — A criminal investigation has been launched after the U.S. Air Force reported that drones were spotted flying over English military bases, a British official said Wednesday.

U.S. troops in Europe reported a swarm of unidentified drones flying over several Air Force bases in the U.K. in the past week, a sighting that comes amid a growing mystery of UFO sightings near military installations.

Over the past week, unidentified drones have been seen flying over joint U.S.-U.K. military bases in the United Kingdom.

The British military has increased security around four air bases in the country that are used by U.S. forces after "a number" of drones were spotted near them.

Over the last few weeks, a number of drones have mysteriously been spotted over four air bases used by the US Air Force (USAF) in the UK.

Unidentified drones have been spotted flying over four bases used by the United States Air Force in Britain, prompting the British government to call in military staff to help protect the sites. The U.