In Hatchet by Gary Paulsen, how does the plane find Brian?

At the end of the story, the plane manages to pick up a distress signal sent by Brian's emergency transmitter.
In Chapter 19, Brian savors the contents of the survival pack. Among other things in the pack, there is a sleeping bag, a foam sleeping pad, an aluminum cook set, a first-aid kit, a fishing kit, a rifle, two bars of soap, and numerous food packets. The emergency transmitter is encased in a plastic bag. Brian doesn't initially realize what it is; he turns the transmitter switch back and forth, and when it makes no sound, he puts it down.
Meanwhile, because he has unwittingly turned on the transmitter and released the antenna on the side of the device, Brian is soon found by a pilot flying nearby. Essentially, the transmitter's distress signals were picked up by the plane, and this is how Brian was found by a "fur buyer mapping Cree trapping camps for future buying runs."