Final answer:
When ESCAT is implemented, the correct system is 'First-come, first-served', which handles aircraft in the order they arrive/request service, providing a fair and efficient way to manage air traffic during emergencies.
Step-by-step explanation:
The question pertains to ESCAT, which stands for Emergency Security Control of Air Traffic. When ESCAT is implemented, the correct system of priorities to ensure optimal use of airspace is First-come, first-served. This means that aircraft are handled in the order that they arrive or request service, without any random assignments or based on alphabetical order, and certainly not based on any escatological principles, which is a typo that should refer to 'eschatological', relating to the end of the world or the final events in human history, which is not relevant here.
The system of 'first-come, first-served' is commonly used in various aspects of air traffic management and ensures a fair and efficient means of handling air traffic without bias. Implementation of ESCAT procedures occurs during times of national emergency, and the focus is on maintaining the safe and orderly management of air traffic rather than on priorities that could create unfair advantages or confusion. Therefore, when ESCAT is active, aircraft are generally handled in the order that they arrive or are detected, consistent with maintaining safety and operational efficiency in the air traffic control system.