He's quite a fan of aviation. At Paine Field in Everett WA (also a Boeing factory site), Allen has a WW2 war birds collection.
His intent was to show how flight technology changed during WW2. There are fully restored and flight capable aircraft from all the major countries involved in WW2.
He is now including armored vehicles as well, from all the combatants.
Did he ever finish the purported Howard Hughes’s ME262? I think Allen is the guy who bought it.