Actually, I think the Germans had ADVANCED "Flying V" jet planes, that US Army captured at the end of WWII; they were modified by USAF and seen flying around Mt. Washington, seen as being disc-shaped objects... GERMAN "Bats". Had books on it years ago. German HORTEN BROS were into it... Horten HO 229 was BIG!
I've Read about & heard the "Foo Fighter" Stories.
But My opinion is split between U.f.O. were maybe researching Fighting here.
Or Time Travelers changing History.
Perhaps Japan or Germany won WW2 the first time around.
Perhaps doing so caused Near destruction of Life here on Earth,
because of Advancements Beyond our dreams & Time Travel was Perfected.
and used in ways it shouldn't
Perhaps someone decided History needed to be Changed.
Came back Messed with the Fighting
Changed History, And not only Letting the U.S. , Russia, and England win the War,
But also caused the invention of Time Travel to Not be invented.
Changing History to what it is Now Permanently.
Yes Sci. Fi. ? Probably I watched too much Science Fiction
But What If ?
You know there are the Holier then thou who Claim if Time travel were invented,
They'd go back and Kill Hitler .
imo Not a good thing to Mess with Past History.
unless it's on the last Day of Earth. as a Last Ditch Effort to save Humanity as a whole.
But as far as Germany or Japan being that advanced back then.
How would they have Lost the War ?