What is the typical format of a Center-to-Center coordination message?

• A. Flight plan, weather, fuel, and maintenance status.
• B. Aircraft color, pilot name, airport, and weather.
• C. Ground speed, heading, and QNH.
• D. Aircraft identification, routing, altitude changes, and sequencing information.

Answer: (D)

Center-to-Center coordination messages are designed to ensure a safe handoff of an aircraft between en route centers by conveying the essential flight information needed to continue separation and sequencing. The key items are who the aircraft is (identification), where it is going and which path it should follow (routing), what altitude changes are planned or requested (altitude changes), and how it fits into the traffic flow relative to other aircraft (sequencing information). This combination lets the receiving center accurately identify the aircraft, anticipate its trajectory, maintain vertical and lateral separation, and slot it correctly in the current stream of traffic.

Other data such as general flight plan details, weather, or maintenance status may be important for overall flight management, but they are not the core elements required for the en-route handoff between centers. Likewise, dynamic parameters like ground speed or heading are situational, whereas the identified set—identification, routing, altitude changes, and sequencing—provides the necessary framework for safe and continuous coordination.