Systems and methods may be used for monitoring and identifying failure in flight management systems. For example, a method may include: calculating, using a first flight management system, a first value of a guidance command for controlling an aircraft for an RNP AP procedure; receiving a second value of the guidance command from a second flight management system; comparing the first value with the second value to determine whether the first value matches the second value; upon determining that the first value does not match the second value, using a flight management system monitor to determine, from the first flight management system and the second flight management system, a flight management system that has computed a correct value of the guidance command; and generating a message indicating that the determined flight management system is to be used to guide the aircraft.