What was Brian's plan if he ever heard a plane engine roar overhead in Hatchet?

Brian plans to have a fire ready so that he can wave a burning limb at a plane if he hears it.

When Brian’s plane crashes in the Canadian wilderness, he is alone because the pilot is dead.  Brian has to use all of his skills and intelligence to survive on his own.  He needs to find a way to get food and shelter, but his next concern is rescue.

Brian is worried that he will not have a way to contact planes that fly over him.  He decides to use fire.

Initially he had thought of making a signal fire every day but he couldn't….  So while he was working he decided to have the fire ready and if he heard an engine, or even thought he heard a plane engine, he would run up with a burning limb and set off the signal fire. (Ch. 11)

Brian tries to figure out how to make a spear out of a stick and use it to fish.  He does find berries to eat, but that does not work out well.  He is mostly concerned about not being rescued.

Brian doesn’t have to wait long to hear a plane.  Brian hears a plane one day and desperately tries to get to his fire fast enough to contact it.

He had to get fire up on the bluff and signal them, get fire and smoke up. He put all of his life into his legs, jumped logs and moved through brush like a light ghost, swiveling and running, his lungs filling and blowing and now the sound was louder, coming in his direction. (Ch. 12)

The plane keeps going, and Brian is not able to make contact.  Brian is sure that it is a search plane.  He is devastated, convinced that they won’t come back and he will never be rescued.  He feels changed because “the disappointment cut him down.”  He makes a new fire that is smokier.

Eventually a plane does come and find Brian, the pilot telling him that he heard his emergency transmission and saw the crashed plane.  Brian is finally saved. His persistence has paid off.