I've always had the suspicion Assange was brought to Ramstein/Landstuhl. If there were health issues. Landstuhl is very secure; Benghazi casualties were there. Short hop from Mildenhall/Lakenheath to Ramstein, too, so no biggie there.
On the night of POTUS flight to Singapore there were planefags reporting AF1 type aircraft out of Ramstein and in Aviano. Speculation on that night was a VIP transfer.
So, just for more speculation and what the fucks; who was in the "beast" when POTUS showed it off to Kim? Assange sitting there would have shown Kim the cabal was no longer a factor.
Again, wag speculation, I know, but just when you think things can't get any crazier, they always seem to do.