Are mystery drones above US bases in England something sinister?

Airspace around US airbases in Norfolk and Suffolk has been under scrutiny following multiple recent drone incursions. Those responsible for the aircraft have yet to be found and nearby residents have questioned how and why the incidents have been allowed to happen.
Drone incursions were initially reported at three US airbases – RAF Mildenhall and RAF Lakenheath in Suffolk, and RAF Feltwell in Norfolk – between 20 and 22 November, and the aircraft has since reappeared.
In the village of Beck Row, Suffolk, which is situated next to RAF Mildenhall, residents reported brightly lit aerial vehicles hovering above their houses and over the base itself.