ZAE is responsible for separating what types of aircraft?

The responsibility of ZAE primarily lies in ensuring safe and efficient air traffic management within its airspace, particularly concerning the separation of aircraft. The correct answer focuses on the separation of departing aircraft from arriving aircraft that are still within their controlled airspace. This is crucial because it prevents conflicts between aircraft that are on different flight paths and ensures smooth transitions for both departures and arrivals.

ZAE must maintain adequate separation to prevent potential collisions and to facilitate the orderly flow of air traffic. The management of this separation is based on various factors including altitude, speed, and geographical locations of the aircraft involved.

The other options misrepresent ZAE's specific responsibilities. All aircraft within ZAE airspace would imply continuous monitoring and separation of every single flight regardless of their phases, which is an overly broad interpretation. Only aircraft preparing for landing would not encompass departing aircraft, which is a critical aspect of air traffic control in a busy terminal airspace. Separating departing aircraft from off-system traffic does not reflect the typical operational priorities of ZAE, as it typically regulates the traffic closely tied to its own airspace management.