Final answer:
An access control officer is responsible for controlling access to the Security Zone of an airport, which is the area where screening and authorized access are most critical.
Step-by-step explanation:
An access control officer is responsible for managing entry and exit at certain points of a secure area to ensure safety and security. In the context of an airport, the area that an access control officer typically controls access to is the Security Zone. This area includes the portions of the airport terminal where travelers are screened and access is restricted to authorized personnel and ticketed passengers. The officer's duties may extend to other sensitive areas, such as the runway or customs area, but their primary focus is on the screening checkpoints and other critical sectors within the security zone to maintain airport safety and operations.