ATC services should be provided on what basis?

Air Traffic Control (ATC) services are designed to manage air traffic effectively and safely, balancing various factors to ensure the safe and orderly flow of air traffic. The principle of providing services "first come, first served" emphasizes prioritizing air traffic based on the time of arrival at a specific point, which helps in managing congested airspace and ensuring fairness among aircraft operators.

This approach allows controllers to handle requests and provide clearances to aircraft based on their operational needs and timelines. It is particularly vital when airspace is busy or when multiple aircraft are competing for the same resources, such as landing at a destination airport or passing through airspace. While factors like aircraft size or military priority could influence decisions in some contexts, the foundational method used in ATC prioritization is based on when an aircraft makes its request, which is crucial for maintaining order and minimizing potential conflicts.