Ground and flight deck alternatives for terminal merging, sequencing, and spacing for arrivals

Aircraft approach the terminal area on different arrival paths, merge and ultimately arrive at capacity-constrained runways on the ground. Upon entering the terminal area, air traffic control manually controls the aircraft in order to merge and sequence arrivals on different paths, and establish longitudinal spacing between aircraft. These operations are termed merging, sequencing, and spacing operations. New technologies available in air traffic control facilities and in the flight deck create the possibility of improving on the manual operations used today. Several alternatives are currently in operational trials. Unclear is what alternative will prove to be most desirable for implementation. This paper seeks to enumerate some alternatives, and their characteristics, and establishes a framework for assessment.