The breakthrough in non-jet propulsion supposedly came in the late
'80s/early '90s with FFX (Field Effects) but there is still debate
over who invented it- either the British or US. At that time there was

Actually breakthrough should have come in before April 1945.
The Article appeared in Eighth Army News on 28 August 1945 had following title
"Nazis had 10000 mph Atom plane,in theory".
(Apparently before the start of Cold War such things could appear in official
US military papers).

Surely Brits did some very fruitful work of their own in this subject,I could
remember ground breaking research work carried out by Aviation Studies Ltd and
Gravity Rand Ltd. in 50s,but American efforts were almost entirely based on
German studies and scientists.
US companies like Glenn-Martin ,Clark.Lear Inc,North American,Sperry-Rand all
had secretive departments working on electrogravity and all of them had Germans

(many of them were from Kammlers SS Advanced weapons research)

But I tend to rule out the Belgian Wave sightings
because Firefly II didn't fly until recently (at the time of the

I would not be so sure as we know that Germans knew as early as 1945,at least
in theory,properties of "Belgian Triangle?"