When overtaking another aircraft flying in the same direction, to which side must the overtaking aircraft alter course to pass?

In aviation, when an aircraft is overtaking another aircraft that is flying in the same direction, the standard procedure is for the overtaking aircraft to alter its course to the right. This rule is established to provide a clear and predictable path for both aircraft, minimizing the risk of collision.

The reasoning behind altering course to the right primarily stems from the convention that most aircraft will maintain a right-hand traffic pattern. By turning right, the overtaking aircraft can more easily monitor the position and actions of the aircraft being overtaken, ensuring that they maintain safe separation. Additionally, operating this way aligns with the general principles of navigation and communication in the aviation industry, which favor right-sided movements for convenience and clarity.

This procedure is reinforced by the International Civil Aviation Organization (ICAO) regulations and guidelines, which aim to standardize operations internationally for safety reasons.