Final answer:
The question seems to be based on a misunderstanding, as it references Brian when the scenario provided is about Antônio and Ahaya on an airplane. Ahaya is walking to prevent blood clots, not because of a fear the plane might do something.
Step-by-step explanation:
The question refers to Brian's fears while he is inside a plane, from the novel 'Hatchet' by Gary Paulsen. The character Brian doesn't fear the plane doing anything in particular as the scenario provided doesn't mention Brian nor his fears. Instead, we learn about another passenger named Antônio who interacts with a man called Ahaya.
Ahaya explains that he is pacing up and down the airplane aisle to prevent the formation of a blood clot in his legs, not to accumulate steps on a pedometer. This preventive measure against deep vein thrombosis, or DVT, is a health concern during flights due to prolonged periods of inactivity that can lead to the development of blood clots.