Method and apparatus to provide a flight path to an aircraft

The method involves automatically determining a decision point (5) which indicates a recent position of an aircraft (A) along a main trajectory (TP), where an optional trajectory (TO) can be activated to permit the aircraft to follow the trajectory (TO). The point is automatically presented to a pilot of the aircraft. The pilot activates the optional trajectory according to the presentation of the point. Independent claims are also included for the following: (A) a device for providing a flight trajectory to an aircraft (B) an aircraft comprising a guiding system which includes flight trajectory providing device.