I can tell you that unless things have changed, Cosby not only has a plane, he has 2 planes.
How do I know this?
Being a pilot myself, I was in a small airport in Turner Falls Ma, a while back, not far from the home that Cosby owns in Shelburne Falls, when a Pilatus (large single engine aircraft) landed. I was talking to the Airport Manager at the time, and he told me it was Cosbys plane. About 10 minutes later a BMW drove up and Cosby got out of the car and came inside, talked to us for about 15 minutes, and took off. He was flying to Manchester NH to board his Gulf Stream (business jet), heading to Los Angeles. The reason for the two planes, was, the smaller airports like Turner Falls have shorter runways not long enough for a Gulf Stream to land.