I've stayed away from the whole UFO topic because I've never seen one (though I do know a lot of credible people who have seen some strange moving objects in the sky.)
But what I do know is that German aeronautics (and science in general) was very advanced during the Nazi era and much of their best stuff never made it to production. I also know that the cream of Germany's aeronautic expertise was absorbed by the US after the war.
It also happens to be true that the whole UFO phenomenon didn't really take off until a few years after World War II.
One strange thing: The head of Germany's secret weapon program and a massive transport plane under his command disappeared after World War II.
I don't know what to make of it all, but there are a lot of indisputable facts and circumstantial evidence that give me pause.
Finally, anyone who thinks that the military can't keep secrets, even massive ones, is crazy.