System and method for assisting with the navigation of an aircraft

The system (1) has an inertial navigation center (3) for providing aircraft positional information partially from accelerometric and gyrometric measurements, and a satellite positioning module (5) to determine another aircraft positional information from satellite positioning data received by a satellite navigation data receiver. An estimation unit formed by the center and a localization module (9) estimates a localization of aircraft at estimation time based on the information. The localization is determined independently from the data received in a preset time interval preceding the time. The aircraft positional information is a Global Positioning System (GPS) data. The time interval is equal to a time to alert. An independent claim is also included for a method of navigation assistance of aircraft.