I really meant that sound is not fast relative to the speed of light. With this idea of a whistle, you need as much advanced warning as possible. There is not one fraction of a second that can be delayed.

Light (vision) would NOT be fast enough for a jogger, who doesn't have super powers, to process the information and to run completely outside of the crash zone. By the time the jogger realized the plane was coming straight toward him, the plane would be maybe 3 seconds away. At that point the jogger would have to sprint maybe 100 meters in about 3 seconds to get outside of the crash zone. Further, the jogger would have to make sure to run those 100 meters perpendicular to the line of flight to avoid the crash. Since vision (light) isn't fast enough, sound isn't fast enough.

As an analogy, when watching a soccer game in a stadium, the sound of the soccer ball gets to the viewer about one second (or more) later. In the ridiculous scenario of the plane crash, the time delay would be even longer because the plane is farther away. That's extra time that the jogger could not afford to spare. Further, the crashing plane would be traveling a lot quicker than a soccer ball.