Llanerchymedd, despite the multiple witnesses etc (contemporary reports from both FSR and BUFORA
here) really does feel like the witnesses saw something military, or perhaps an exercise involving RAF Search and Rescue or something like that.
The description of one of the entities waving its arms over its head, in the international (or intergalactic?) gesture for "over here mate", suggests a helicopter picking some people up; some of the descriptions given of the lights (silent, slowly descending) also suggest a flare, perhaps deployed as a location signal.
RAF Valley emphatically denied that they ever held "off-base exercises", but along with the possible RAF inspiration of several of the Broad Haven events I can't help but wonder if there was in fact a programme of off-base exercises in the period, which may have fed into this Welsh 'flap'.