Project Blue Book Case #2136. On September 29, 1952, an unidentified object was reported over England — observed by U.S. military personnel stationed in the United Kingdom. The UK hosted numerous American air bases including the major B-47 bomber stations at Brize Norton, Lakenheath, and Mildenhall that formed the forward edge of SAC's European nuclear strike capability.
September 1952 was during the great wave, which had now clearly extended to American military installations across Europe and the UK. The case was classified "Unknown."