In RNP airspace, how often should the FMS position error be less than the RNP value?

In RNP (Required Navigation Performance) airspace, the standard stipulates that the Flight Management System (FMS) position error must be less than the designated RNP value 95% of the time during operation. This benchmark is crucial for ensuring that aircraft maintain a high level of accuracy and safety while navigating through this specific airspace. The requirement emphasizes the importance of predictable and reliable navigation performance, which is vital for safe operation, particularly in areas of increased traffic or where precise flight paths are necessary.

The 95% figure reflects a balance between operational flexibility and safety, allowing for occasional deviations from the ideal performance measure without compromising overall safety. RNP values indicate the level of precision required for navigation, and meeting this 95% standard helps ensure that aircraft are capable of flying safely along their intended routes.

Other options suggest higher compliance rates (like 98% and 100%), which could impose unrealistic operational limitations on pilots and airlines, potentially causing inefficiencies in air traffic management or flight operations. The 90% option, while it represents a good standard, falls short of the rigor required in RNP airspace standards, where precision and reliability are key. Therefore, the requirement for the FMS position error to be below the RNP value