Local magnetic disturbances can affect compass readings by causing deviation. Deviation occurs when the Earth's magnetic field is distorted by the metal and electrical equipment in and around the aircraft. This distortion causes the compass needle to deviate slightly from magnetic north, indicating a direction known as compass north.

The difference between the direction of magnetic north and compass north is called deviation. Factors such as the aircraft's magnetic fields, magnetic latitude, heading, and changes in electronic equipment can all contribute to this deviation.

If we ignore the effects of the local magnetic disturbances, the aircraft's compass should point the magnetic North.