I'd add the Tank Museum at Bovingdon, UK to that - though it's a long way from the airports if you are from somewhere (like the UK...) that doesn't believe in driving long distances.
I remember going to Overloon as a scout on my first overseas trip circa 1985 (hard to forget, the museum parrot bit me!) - I hope someone, somewhere, has photos of it from that sort of time as it was a very strange place, looking back now. Much of the collection was outdoors, and some of it had been there since the warring parties left it in 1944. Great for atmosphere, with red squirrels playing round the Giant Wurzberg radar aerial, but not so good for preservation of exhibits - especially aircraft - though Spitfire XI PL965 that I saw (looking very ratty!) there has been restored to fly, and I've seen it again in the air.