Which phraseology is appropriate for instructing an aircraft to taxi?

The phraseology "Proceed to hold short of the runway" is the correct instruction for guiding an aircraft to taxi. This phrase clearly communicates to the pilot exactly where to taxi, ensuring that they maintain a safe distance from the runway where takeoffs and landings occur.

The instruction is structured to enhance safety protocols in busy air traffic environments, as it explicitly tells the pilot to stop before reaching the runway. This is crucial in preventing runway incursions, which could lead to dangerous situations.

In contrast, the other phrases do not effectively convey the required taxiing instruction. "Taxi on all surfaces only" is ambiguous and does not provide a clear destination or safe stopping point. "Clear for takeoff on all sites" is unrelated to taxiing instructions and instead indicates takeoff clearance, which is a different phase of flight. Lastly, "Move to any runway desired" lacks specificity and could lead to confusion or conflict on the ground, as it does not designate a particular runway and assumes the pilot has an understanding of the surrounding traffic.

Thus, by using precise language instructing the aircraft to hold short of the runway, air traffic controllers ensure both clarity and safety in operations.