The Reaper is operated by RAF personnel based at Creech in Nevada.
Armed-forces personnel based in London and elsewhere were ordered to be more vigilant.
Six months ago, the Department of the Navy introduced a campaign to alert personnel based overseas to the threat.
Maureen Farrell, 40, and Whitney You, 35, are physicians and active Navy personnel based in San Diego.
RAF Upwood (Cambs) Provides accommodation and support services for personnel based at RAF Alconbury and RAF Molesworth.
It also risks bringing the US into a more direct confrontation with Syria in defence of its Kurdish allies and American personnel based alongside them.
There, we met Gisela Budenz, owner of a cafe that once served as a gathering spot for American troops and civilian personnel based in Fulda.
The authorities say the attacks may have been carried out by police officers or military personnel, based on the stealth and accuracy with which the victims were killed.
Opposition is most vociferous in Pakistan, where the government said on Wednesday it was shutting down a big CIA drone base, and had ordered US personnel based there to leave.
"Since I, the 'curator,' choose personnel based on a particular aesthetic, I am able to think of creative ways of presenting music beyond the traditional 'call-up a venue and ask for a gig' way of presenting".
Also Sunday, George Osborne, the British chancellor of the Exchequer, said that Britain would compensate British government and military personnel based in Cyprus whose finances would be affected by the levy.
