Final answer:
Follow the procedures outlined in the Lost Communications section of the aircraft's operating manual or regulations to navigate and land safely.
Step-by-step explanation:
In the given scenario, if communication with ATC has been lost and all attempts to re-establish communications fail, the appropriate action to take would be to follow the procedures outlined in the Lost Communications section of the aircraft's operating manual or the specific regulations of the governing aviation authority. These procedures typically involve adhering to a predetermined course of action and using navigational aids such as radar vectors, NDBs, and LOMs to navigate and land safely. The specific steps would depend on the aircraft type, the airport facilities, and the prevailing conditions.