Why Equity Is so Elusive: Dynamical Properties of Overscheduled National Airspace System (nas) Resources

One of the major issues in the proposed concepts-of-operations for NEXTGEN is the equitable allocation of available National Airspace System (NAS) resources when demand is in excess of the capacity of the resource. NAS resources include airport and airspace slots allocated to flights from different airlines, carrying passengers and cargo from different geographic areas, affecting local air and water quality, and choosing different strategies for utilization of fossil fuels that affect global climate change. Although federal regulations, Congressional policies, and modernization plans call for equitable allocation of publicly held resources, the mechanisms for equitable allocation, and the trade-offs that must be made between stakeholders, exhibit a high degree of social, political, and economic complexity. Further, the allocations that are routinely made in Traffic Flow Management (TFM) and Air Traffic Control (ATC) are subject to widespread perceptions that the allocations are not systemically equitable. The purpose of this paper is to establish the underlying properties of overscheduled resources and the associated limits on equitable allocation. These theoretical results should form the starting point for the development of feasible, robust, sustainable, NAS policies. This paper describes the dynamic properties of a deterministic queueing model when demand for a resource is scheduled in excess of its capacity. The model demonstrates that (i) a natural asymmetry exists in the allocation of over-scheduled resources due to a “spill-over effect,” (ii) this asymmetry results in a low probability (< 10%) of an equitable allocation of resources amongst groups of flights (e.g. airlines), and (iii) increased competition reduces the feasibility of equitable allocations. The implications of these results are that the equitable allocation of a resource scheduled by independent groups (i.e. airlines) is very difficult to achieve. Expectations for equity in modernization plans should be tempered to meet this reality. These and other implications for planning, policy, and operations in a next-generation NAS are discussed.