When is an altitude readout considered valid?

An altitude readout is considered valid when it varies less than 300 feet from the pilot's reported altitude. This guideline is based on the acceptable margin of error in altitude reporting systems, accounting for potential discrepancies between the altimeter readings and what the pilot has reported. In practice, this ensures that the air traffic control systems can rely on the reported altitude while maintaining safe separation between aircraft.

The idea behind this threshold is to create a buffer to accommodate minor deviations that may occur due to atmospheric conditions, instrument errors, or differences in the altimeter settings used by different aircraft. So, when an aircraft's altitude readout falls within this 300-foot variance, it confirms that the information is trustworthy and aligns closely enough with the pilot's situational awareness.

Other choices reflect different concepts that do not pertain to the validation of an altitude readout in the context of air traffic management. For instance, matching the altitude reporting from an aircraft's flight plan could indicate that the aircraft is following its intended route, but it does not validate the accuracy of the altitude being reported in real-time. Consistently being above a minimum safe altitude is crucial for flight safety, yet it does not confirm the validity of any specific altitude readout. Lastly, having no prior