Although most birds have the characteristics of small size and light weight, the speed of airplane flight is really great. The relative speed between the plane and the bird is very high. According to the momentum theorem, a bird with a weight of 0.45 kg will generate a force of 1.500 Newton when it collides with an airplane with a speed of 80 kilometers per hour, and a force of 2 1.6 million Newton when it collides with an airplane with a speed of 960 kilometers per hour. High-speed relative motion makes the destructive power of birds reach an alarming level.

Aircraft navigation systems are mostly located in the front, including airborne radar, electronic navigation equipment, communication equipment and so on. Collision with birds causes the plane to lose the guidance of the navigation system and is prone to accidents.

The collision with birds has more direct consequences for the destruction of power system. For propeller aircraft, bird impact will lead to blade deformation or even fracture, reducing the power of the aircraft; For jet aircraft, birds are often sucked into the air intake, which will deform the blades of the turbine engine, stop the engine and even catch fire. This kind of damage is often fatal, which will directly lead to the stall and crash of the plane.

So planes are most afraid of hitting birds.