The Pentagon is “actively” watching for drones over U.S. Air Force locations in the United Kingdom, following a series of unexplained sightings over the past two weeks. The sightings, which took place over three U.S. air bases last week between Nov. 20 and 22 and again on Monday night, have prompted the deployment of roughly 60 British troops, including counterdrone specialists, to help defend the locations, according to Sky News. While installation leaders have determined the drones so far have not impacted the bases, personnel or military assets held there, Pentagon press secretary Maj. Gen. Pat Ryder told reporters Tuesday that officials take the sightings very seriously. “They are being actively monitored,” he said of the unmanned aerial vehicles (UAVs). “It’s something that we're going to take seriously. We're continuing to look into it, but as of right now, [it] has not had any significant mission impact.”  He added that the U.S. military continues to work with U.K. authorities and mission partners to ensure the safety of personnel, facilities and equipment, but he did not go into specifics as to the number of British troops deployed to help out.  U.S. troops in Europe last week reported a swarm of unidentified drones flying over the Air Force bases Feltwell in Norfolk and Mildenhall and Lakenheath in Suffolk, the latter being the only home for America’s F-35/F-15 fighter wing in Europe. In a Monday statement, the U.S. military said the number of drones fluctuated and ranged in size and configuration. The incidents come amid growing questions over unidentified aerial phenomenon sightings or unidentified swarms of drones near military installations, including drones that flew near Virginia's Langley Air Force Base in December 2023. In that series of events, which was not publicly revealed until last month, a fleet of unidentified aircraft flew over Langley Air Force Base as well as over the area that includes the Navy’s SEAL Team Six home base and Naval Station Norfolk, the world’s largest naval port, over 17 days. None of the drones were shot down, even as they flew in restricted airspace, as federal law prohibits U.S. forces from shooting down such aircraft near military bases in the country unless they pose an imminent threat.  In another sighting in October 2023, five drones flew over a government site used for nuclear weapons experiments for three days outside Las Vegas. It is not publicly known who operated them. And U.S. officials confirmed in October that unidentified drone swarms were spotted in recent months near Edwards Air Force Base, Calif., north of Los Angeles.  Asked whether the UAVs spotted over the U.S. airfields in the U.K. are linked to last year’s drone sightings, Ryder said he did not want to “speculate and draw unnecessary connections.”  Questioned why no drones were shot down, he said the U.S. military has “a variety of means at our disposal” to protect our personnel and our facilities and “always maintain the right to defend ourselves if we deem something to be a threat.”  But he added that officials do not want to risk “inadvertently creating second-, third-order effects — in other words, potentially harming the civilian communities in which we operate in and around.”