The twin-engine F-15C Eagle went down about 9:40 a.m. local time about 74 nautical miles off Flamborough Head in East Yorkshire.
“The aircraft was from the 48th Fighter Wing, RAF Leakenheath, United Kingdom,” the Air Force said in a statement to The Sun.
“At the time of the accident, the aircraft was on a routine training mission with one pilot on board,” it said, New York Post reported.
“The cause of the crash as well as the status of the pilot are unknown at this time and UK Search and Rescue have been called to support,” the statement added.
Citing a flight tracker website, Sky News said the jet circled in the area before disappearing.
A coast guard spokeswoman said, “The HM Coastguard helicopter from Humberside has been sent along with Bridlington and Scarborough RNLI lifeboats.
“Following a Mayday broadcast by HM Coastguard, other vessels nearby are heading to the area,” she added.
RAF Lakenheath, the largest US Air Force-operated base in England, is home to its only F-15 fighter wing in Europe. More than 4,000 US service members are stationed there.