How come you can not see people in the google satellite images or maps?

google imagery is updated often and even if a plane is caught in flight on a given image -the next update for that area will no longer have the plane. google Earth is more suited for seeing planes in flight especially with its 'Historical Imagery' so you can return to a particular place and time to see a plane caught in flight.

The short answer is that you can see planes in flight on google Maps and google Earth. The long answer is that I am sure google data is pulled from both satellite data and "flown" images. Flown images are taken at lower altitude so commercial planes are likely routed over the one taking the images.