Airspace Fairness: Rarely Discussed, But Foundational to the Adoption of UTM

With a myriad of new Uncrewed Aircraft Systems (UAS) taking flight, ensuring fair airspace access is a growing concern in the Air Traffic Management (UTM) ecosystem. Managing traditional air traffic typically employs a first-come, first-served approach; however, the diversity of use cases for Uncrewed Traffic Management (UTM) require more innovative approaches to prioritization, even in these early stages of UTM development, to avoid inequity and added costs that result from delaying implementation.

Traffic management approaches that emphasize fairness in the early stages of UTM development will serve the diversity of UTM operations and offer equitable and effective alternatives to the basic approaches to prioritization proposed in most UTM systems.

Unique Solutions

Fairness, at its core, is equitable airspace access. It is achieved by balancing disparate individual, social and commercial needs to determine airspace access priority and manage potential conflicts. Because UTM airspace is expected to become more congested, speedy, automated traffic management solutions are critical.

Ensuring fairness in UTM is especially important because of its unique infrastructure. While traditional air traffic management operates under the direction of a centralized management and control authority, many proposed UTM systems adopt a decentralized approach served by a network of entities to manage traffic based on shared data and common regulations.

This unique architecture requires similarly unique traffic management solutions. Traditional air traffic management’s “first-come, first-served” approach works because today’s flight plans are not deconflicted preflight, and the air traffic is relatively homogenous – transporting people or cargo from one place to another. That approach has evolved to “first-requested, first-served” in most UTM systems because flight plans are deconflicted at request, and the diversity of use cases in UTM makes it difficult to find a common definition of “first-come”. First-requested, first-served, however, becomes increasingly inadequate as the ecosystem grows and operation types increase, becoming more varied. Depending on how it is implemented, the approach leaves operators that cannot file early, like on-demand delivery services and air taxis, unfairly disadvantaged. And as emergency and news services, among others, make increasing use of UAS technologies, the diversity of operators will continue to expand.

Early Implementation

This growing variety of operators means implementing fairness in the early stages of UTM’s development is critical. While existing traffic may be manageable now, addressing issues of fairness proactively prevents the need for significant (and costly) system redesign in the future. And while it is convenient to expect operators to approach airspace and related resources equitably from the start, history suggests otherwise. Addressing fairness now discourages early movers and industry giants from gaming this, relatively, young system.

Because of this, Airbus UTM has emphasized fairness in UTM, collaborating with the Massachusetts Institute of Technology on research for industry standardization. The research shows, in part, that early collaboration is key to effectively integrating fairness in UTM’s architecture. In order for this environment to function, operators must view their access to airspace and related resources as fair. If these entities consider the system unfair, they may withdraw their cooperation at the expense of system efficiency.

Collaboration is not a new concept in air traffic management. In the mid-1990s, for example, the Collaborative Decision Making (CDM) initiative was employed within the Federal Aviation Administration with two central tenets: better information leads to better decisions, and members of the aviation community should have the tools and information to respond to changing conditions. The initiative brought representatives together from all sectors of the aviation community to share information and offer solutions, and it is now integral to the performance of today’s air traffic management. Because of UTM’s federated approach, a similar emphasis on collaboration is necessary, especially in the early stages of refining UTM’s architecture.

Quantifying Fairness

As part of its research, Airbus UTM is developing the concept of a Fairness Engine. The concept’s approach is twofold: monitor flight operations by gathering fairness-relevant information from operators and service providers, and automatically apply that information in the event of traffic management conflicts to determine priority in a way that is fair.

Among other factors, the monitoring function considers the cost of traffic management on an operator. One way to measure this is the delay the operator experiences beyond what they would experience if they were the only one seeking airspace access. The monitoring function assigns a fairness metric to the flight operation based on the calculation of this cost. The second function, prioritization, initially determines priority for conflicts based on operation type – emergency services before passenger and package delivery services, for example – but, in the event of a conflict between two operations of the same type, the program can apply the metric assigned by the monitoring function - or another metric - to resolve the conflict and determine priority. The engine can also be programmed to accommodate other fairness metrics that a user considers most beneficial.

Elements of the Fairness Engine approach are currently being used to integrate fairness in at least one of the UTM systems in development worldwide. And while continued research is needed to further explore specific fairness metrics, adopting fairness as a guiding principle now not only provides an equitable and effective approach to traffic management, but it serves the continued development of UTM’s unique architecture and mitigates the inequity and ensuing system-wide costs that result from delayed action.

- Scot Campbell