"I believe most occur with 5 miles of an airport and most often on clear beautiful days..."
Uh, yes, that describes the situation last Sunday when I got an excessively good look at an RV-6 while on a 45 deg entry to downwind at our airport. I was descending out of about 1100 ft to the 1000 ft AGL pattern altitude, and as usual trying to understand the foreign students in the pattern when the RV-6 suddenly appeared from my left, maybe 50 feet above me at most and about 100 ft away. I dove to 900 ft to make sure I was clear of him. He obviously was cruising along, enjoying the beautiful weather, oblivious to cutting through the traffic pattern of an airport and obviously not listening to the correct radio frequency.
But the best mid-air story I ever heard, by far, was Tony Levier describing how he was flying a P-38 one day and collided with an F4U being piloted by none other than Joe Foss.
Thanks for the P-59 story!