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

Here is an example of "world's only flying" piece, in this collection.

Thats a massive collection

http://www.businessinsider.com/paul-allen-vintage-plane-collection-2014-10?op=1