This is an incorrect premise. The sound of an aircraft will always appear to be coming from the front of the plane, not from behind it. When an aircraft flies overhead, the sound waves it produces travel through the air at the speed of sound. As the plane is moving forward, it is also pushing air in front of it, creating a denser pocket of air. This denser air causes the sound waves to travel faster and reach your ears first, making it seem like the sound is coming from the front of the aircraft.