When taxiing at a tower-controlled airport, what must you receive to cross each runway?

To safely cross each runway at a tower-controlled airport, a pilot must receive clearance from the tower controller. This requirement is in place to ensure that the runway is clear of all traffic, including departing and arriving aircraft, which helps prevent accidents and ensures efficient traffic flow at busy airports.

The purpose of obtaining this clearance is to confirm that the tower has visually observed the runway and that it is safe for the aircraft to proceed. The tower controller is responsible for managing all aircraft movements on and around the runways, making their clearance essential for maintaining safety protocols.

In contrast, permission from the ground controller typically covers movement on taxiways but does not include runway crossings, while notification from other aircraft is not a formal requirement and does not provide the necessary clearance to proceed. Similarly, the idea that no clearance is required is incorrect, as operational safety mandates that clearance from the appropriate authority is always needed when interacting with runways at a controlled airport.