The unmanned aerial vehicles have been spotted multiple times over three bases in the last week.
The mystery began back on November 20th when a number of unidentified drones were spotted over RAF Lakenheath and RAF Mildenhall in Suffolk as well as over RAF Feltwell in Norfolk.
A similar series of incursions was reported on November 22nd and then again on the 25th.
All three bases are leased by the US Air Force.
"[There has been] no impact to residents or infrastructure and [they] have not been identified as hostile," said a spokesperson for the US Air Force's operations in Europe.
"However they are still continuously being monitored to ensure the safety and security of the installations."
"[It is] unclear how many drones are involved, who is operating them and why they are doing it."
According to reports, around 60 British troops and counter-drone specialists have been deployed to the bases in an effort to defend against future incursions.
Pentagon spokesman Major General Patrick Ryder said earlier this week that it was too soon to draw conclusions on who might be responsible for the drones.
Given their co-ordinated nature, however, it seems unlikely to be hobbyists.