One of his biggest passions over the years, however, has been aviation.
When he was young, his father was named the associate director of libraries at the University of Washington.
“I’d spend hours reading about the engines in some of those planes,” Allen told Forbes. “I was trying to understand how things worked — how things were put together, everything from aeroplane engines to rockets and nuclear power plants. I was just intrigued by the complexity and the power and the grace of these things flying.”
Allen started collecting planes and other World War II artifacts in the 1990s. In 2004, he opened his 31-piece collection — rumoured to be worth many millions of dollars — to the public. It’s currently housed in the Flying Heritage Collection, in a hangar in Everett, Washington.