A high integrity navigation system and method are provided. The method comprises performing a cyclic redundancy check (CRC) of a desired flight path of an aircraft, for example an approach to an airport, and comparing the CRC with a stored CRC performed on the identified flight path. If the comparison exceeds a first threshold, a first alert is provided wherein the pilot is to perform a published missed approach. A second alert, also requiring a missed approach, is provided when one or more comparisons are performed of a sensor position of the aircraft with the high integrity flight path; a defined flight path with the high integrity flight path; and the sensor position with an aircraft position determined by a flight management system, and thresholds are exceeded.