You don't have agency over other drivers on the road and they might cause an accident without any fault of yours. That issue is (almost) entirely avoided by planes.
But importantly, I have the ability to see and react and avoid the collision. On the plane, I have the ability to eat lunch. Surely this could be considered a difference in agency.
Just a few weeks ago an American Airlines regional jet went down near Washington, D.C.'s after hitting a helicopter.