Never knew about this side of Paul Allen, only that he was a co-founder of Microsoft. Someone who really cherishes the heritage of aviation. Spent a lot of money on restoring WW2 aircraft, and is one of the only places where many of these are still kept in flying condition.
http://www.flyingheritage.com
http://en.wikipedia.org/wiki/Flying_Heritage_Collection
http://www.youtube.com/watch?v=hgAlwePmDls
Here is an example of "world's only flying" piece, in this collection.
http://www.youtube.com/watch?v=qF9VZSkVZI0
Thats a massive collection
http://www.businessinsider.com/paul-allen-vintage-plane-collection-2014-10?op=1 (http://www.businessinsider.com/paul-allen-vintage-plane-collection-2014-10?op=1)