In Hatchet where does Brian sit in the plane?

Brian sits in the copilot seat of the small plane. 

The plane Brian takes to Canada is a Cessna 406, a very small “bush-plane.”  He is the only passenger.  The pilot is not very talkative either. 

He was thirteen and the only passenger on the plane … [Since] Brian had come to the small airport in Hampton, New York to meet the plane—driven by his mother—the pilot had spoken only five words to him. "Get in the copilot's seat." Which Brian had done. (Ch. 1) 

Brian finds sitting in the copilot’s seat exciting.  After all, he has never flown a plane before and sitting there makes him feel like he is helping fly the plane.  He can see how it works. 

He had never flown in a single-engine plane before and to be sitting in the copilot's seat with all the controls right there in front of him, all the instruments in his face as the plane clawed for altitude, jerking and sliding on the wind currents as the pilot took off, had been interesting and exciting. (Ch. 1) 

Later, the pilot even lets Brian fly the plane a little, teaching him about autopilot and how some of the controls work.  Brian is nervous about this at first, but it is thrilling and interesting.  He will need these skills later when his pilot has a heart attack and Brian has to land, or crash, the plane himself. 

During the plane ride, Brian is not in a very good head space.  He is upset because his parents are getting divorced, and he knows why.  He knows about the affair that his mother had.  He finds it hard to say good-bye to her, because he does not even know what to say or how to be around her.  He is very depressed about the secret he is keeping.