And it could be that big back of seat that the Captain is sitting in?
Backs of seats kill shots and are too intrusive. With a 10mm lens you could stand right beside the seat and still get all the flight deck in with the result being no back of seat. Remember the aircraft has to be the prime subject not the Captain or the back of seat. It would also be better if the Captain was looking forward and a little further left so that he doesnt obscure the instruments. A close call really and not far off being acceptable.
See how you have the RH
seat that is okay, and if you had stood closer the instruments would be bigger in the frame especially with your 10mm lens.
Good things take Time.