When must you coordinate with the appropriate control tower?

Coordination with the appropriate control tower is essential whenever issuing any clearance that falls under tower jurisdiction. This ensures that all operational control measures align with the specific procedures and regulations established for air traffic management. Tower jurisdiction typically encompasses activities related to takeoffs, landings, and any clearances that involve the runway or any areas that are controlled by the tower.

By coordinating before issuing clearances, air traffic controllers can maintain the safety and efficiency of the airspace, ensuring that all required permissions and instructions are given in accordance with established protocols. This previous communication helps prevent misunderstandings and conflicts in air traffic that could arise from a lack of coordination.

Other options refer to specific actions that may not encompass the comprehensive need for coordination found in the correct choice. For instance, coordinating upon noticing an aircraft in difficulty might be a critical action, but it does not address all situations that necessitate prior coordination.