A 15-minute drive south of Ontario at Chino Airport, Planes of Fame is one of the best WWII-era aircraft museums in the country, with a collection of about 150 aircraft, many of them still flyable. The hangars hold P-51 Mustangs, an F4U Corsair, a Japanese Zero (one of the last airworthy examples), a B-25 bomber, and dozens of others.
The first Saturday of each month is "Flying Day" — one of the historic aircraft is taken out and flown for the crowd. Worth timing a visit around. Adult admission around $20.