In the context of aviation and aerospace, an Automatic Call Distributor (ACD) refers to a system or software used in air traffic control and other aviation operations to manage and distribute incoming calls or requests for assistance from aircraft, airlines, or other stakeholders.

An ACD in aviation typically performs the following functions:

1. Call routing: It automatically directs incoming calls to the most suitable air traffic controller or specialist, based on factors such as the type of request, the location of the aircraft, or the controller's workload.
2. Call queuing: If all controllers are busy, the ACD holds the call in a queue and plays a message or music to the caller, ensuring that the call is not lost and the caller is informed of the wait time.
3. Priority handling: The ACD can prioritize calls based on their urgency or importance, such as emergency calls or calls from aircraft in distress.
4. Call tracking: The system may also track call metrics, such as call volume, wait times, and response rates, to help air traffic control managers optimize their operations and resource allocation.

The use of an ACD in aviation can help improve the efficiency and effectiveness of air traffic control operations, reduce response times, and enhance overall safety.