2.2 The Free Flight Concept
Free Flight has been defined (Ref. 1) as:
“... a safe and efficient flight operating capability under instrument flight rules (IFR) in which the operators have the freedom to select their path and speed in real time. Air traffic restrictions are only imposed to ensure separation, to preclude exceeding airport capacity, to prevent unauthorized flight through Special Use Airspace (SUA), and to ensure safety of flight. Restrictions are limited in extent and duration to correct the identified problem. Any activity which removes restrictions represents a move toward free flight.”
The Free Flight paradigm recognizes that users of the aviation system each have their own unique objectives, and require the flexibility to achieve their objectives. The goal is to expand the domains of flight/fleet operations over which the users have the flexibility to self-optimize fleet throughput/connectivity, schedule integrity, and flight efficiency. The ultimate realization of free flight allows each flight to operate as if it were the only aircraft in the NAS. This allows users to optimize a single flight, or for scheduled fleet operators, allows users to manipulate their flights to optimize the fleet operations. ATSP-imposed restrictions would only occur as dynamically necessary, and only to the extent required for safety and system efficiency. Theoretically, the concept of Free Flight provides the users with the ultimate flexibility for self-optimization.
In contrast to Free Flight, today’s system provides relatively little room for self-optimization. The users choose their schedule and routing, but even this is strongly influenced by the ATSP and other operators. Once the flight has been initiated, almost all decisions are made by the ATSP, often with little opportunity to accommodate user preferences. In order to address these issues regarding the current system, many organizations have initiated efforts towards NAS modernization.

2.3 Relationship Between DAG-TM and Other Relevant Activities/Programs
In 1995, the RTCA Task Force 3 developed an implementation plan that represents a roadmap to NAS modernization. This led to various FAA and RTCA Concepts of Operation, ultimately resulting in the joint RTCA/FAA Concept of Operation for 2005. Additionally, in support of a 1997 AATT project milestone, AATT integrated the various concepts of operation into an overall AATT Concept of Operations which provided the vision for all AATT research. The DAG-TM Concept was formulated in the context of enhancing the various Concepts of Operation by adding a greater level of detail to the more “revolutionary” Free Flight applications outlined in the RTCA implementation plan (e.g., collaborative flow management and free maneuvering).
Successful implementation of the DAG-TM concept will require an unprecedented level of distributed decision-making between the components of the ATSP-FD-AOC triad. This high level of distribution will also necessitate a high level of integration between airborne and ground-based systems and tools such as decision support automation, datalink applications, and CNS/ATM technologies.
　
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