What is a recommended way for a controller to relayed clearance to a pilot if direct communication is not possible?

In situations where direct communication between a controller and a pilot is not possible, having another aircraft relay the clearance is the most practical and effective solution. This method leverages the fact that other aircraft in the vicinity can often communicate with both the controller and the pilots in question. By using another aircraft as an intermediary, important information such as clearances, instructions, or advisories can be transmitted quickly and accurately, ensuring the safety and efficiency of air traffic operations.

The other options aren't as suitable; for instance, satellite communication might not be available or reliable in all areas, especially in congested or mountainous regions. Sending a text message could be hindered by technological limitations or the need for immediate action, and waiting for the pilot to land unnecessarily delays their operations and could lead to unsafe situations if the pilot has urgent instructions that need to be followed en route. Thus, relaying clearance via another aircraft is often considered the most efficient and timely approach in these scenarios.