In the event of radio communication failure, what should an IFR pilot use to determine their altitude?

In the scenario of radio communication failure, the pilot should rely on the minimum IFR altitude to maintain safe operations. The minimum IFR altitude is crucial because it ensures that, regardless of communication issues, the aircraft remains at a safe vertical distance from terrain and obstacles, thus enhancing safety and reducing the likelihood of an in-flight accident.

If a pilot were to rely solely on the altitude assigned by ATC or the cruising altitude established during flight, these could present risks, especially if the aircraft were to encounter different terrain topographies or obstacles that were not accounted for during the assignment. The filed flight plan typically does not provide specific altitude guidance for maintaining safety during a communication failure. Instead, minimum IFR altitudes are specifically designed to accommodate such scenarios and provide a safety buffer for pilots navigating through controlled airspace even without radio contact.