What is the function of a document offering direct and guidance for managing airport facilities?

The function of the document that offers direct guidance for managing airport facilities is to provide operational regulations. This document typically lays out policies, procedures, and standards that govern the operation and management of various airport facilities, ensuring safety, efficiency, and compliance with regulatory requirements.

Operational regulations encompass a wide range of topics, including security protocols, noise abatement procedures, and emergency response plans. By adhering to these regulations, airport personnel can effectively manage daily operations and ensure that all airport activities align with national and international standards.

The other choices focus on specific aspects of airport management. Establishing flight routes pertains more to air traffic control and the planning of airspace use. Maintaining airport schedules involves coordinating flight times and gate assignments but does not provide the overarching guidance required to manage facilities as a whole. Overseeing runway maintenance is a critical task within airport management, but it is just one element of the broader operational framework that the appropriate regulations would cover.