If the position disagrees by more than how many NM from the last known position by the FMS, a message displays?

In the context of the PSA Airlines Canadair Regional Jet Systems, the answer of 40 NM is accurate because it relates to how the Flight Management System (FMS) monitors the aircraft’s position during flight. When there is a significant deviation from the last known position calculated by the FMS, it is crucial for safety and operational integrity to notify the flight crew. This notification is triggered when the positional discrepancy exceeds 40 nautical miles (NM).

This threshold is established to help ensure that pilots are immediately made aware of potentially significant navigational errors or other issues that could affect flight safety. By prompting the crew with a message at this range, it provides an opportunity for timely corrective action to be initiated, such as verifying navigation data or reestablishing the correct flight path. This level of monitoring is an essential aspect of modern aircraft systems to maintain awareness of position during the flight, particularly in areas where navigation reliability is critical. Understanding this process enhances a pilot's ability to manage deviations effectively and maintain safety in flight operations.