NASA has developed a unique innovation to compute passed back spacing requirements in air traffic management. The air traffic managers of the National Airspace System (NAS) in the United States regularly implement various Traffic Management Initiatives (TMI) to handle traffic in a safe and efficient manner. One such initiative is the Miles-in-Trail restriction. Imposed Miles-in-Trail is the value of spacing required between aircraft flying along a certain path. They help air traffic managers control the flow of aircraft into and out of an air traffic control facility. Miles-in-Trail can be implemented independently or in conjunction with other TMIs (e.g., a severe weather avoidance plan route, or a Playbook route). This model computes passback restrictions given the imposed constraint, the start and end times, the boundaries at where those restrictions need to be passed back, and the amount of maximum ground and airborne delay allowed.

Generally, FAA managers employ Miles-in-Trail as a traffic management initiative when downstream traffic congestion at airports is anticipated. In order to successfully implement the Miles-in-Trail as airspace fixes or navigational aids, the restriction values need to be computed for passing back to upstream facilities at specific boundaries. When a Miles-in-Trail constraint is imposed at an airspace location due to congestion, some spacing constraints are passed back to upstream air route traffic control centers. Additional operational considerations required by the traffic managers to implement the passback restrictions are maximum ground delay and absorbable airborne delay, both incorporated in this model. The model allows for computation of passback restrictions for current and changing traffic patterns, and for multiple merging streams and dynamically drawn passback boundaries. This model improves upon a previous version using traffic manager feedback, resulting in significant improvements in guidance.

Potential applications include use in air traffic management, airline flight dispatch operations, and aeronautics systems.

NASA is actively seeking licensees to commercialize this technology. Please contact the Technology Partnerships Office at This email address is being protected from spambots. You need JavaScript enabled to view it. to initiate licensing discussions. Follow this link for more information: