What must ZAE do if it is unable to issue the clearance right away for MLU departures?

When ZAE is unable to issue clearance right away for departures from MLU, the appropriate action is to issue an Estimated Further Clearance (EFC) time. Providing an EFC time helps manage expectations for the pilots involved and keeps them informed about when they can expect to receive their clearance. This communication is crucial in air traffic management as it helps prevent confusion, reduces the likelihood of pilots entering holding patterns unnecessarily, and ensures that traffic flows smoothly.

An EFC time not only serves as a guideline for pilots but also allows them to maintain situational awareness while awaiting further instructions. This action aligns with air traffic control best practices, where clear communication is key to ensuring safety and efficiency in the airspace.

In contrast, the other options may not effectively resolve the situation. Establishing a holding pattern or notifying the pilot to hold could be actions taken in specific circumstances but do not directly inform the pilot of when they might receive the necessary clearance. Relay a reminder does not address the specific clearance issue and may not provide pilots with the critical information they require to proceed safely.