Airspace capacity constraints caused by adverse weather are a major driver for enhanced Traffic Flow Management (TFM) capabilities. One of the most prominent TFM initiatives introduced in recent years is the Airspace Flow Program (AFP). AFPs are used to plan and manage flights through airspace constrained by severe weather. Aircraft with filed flight plans through the AFP region have the option of rerouting to avoid that airspace or remaining on a route through the AFP region and enduring the assigned AFP delay.

An AFP operates as a strategic air traffic management tool, where “strategic” (i.e., 4 – 6 hour) weather forecasts are used to determine key AFP parameters such as the program start time and the time rate traffic capacity profile for the program. AFP throughput rates are set for hourly periods and rates are often revisited during bi-hourly Strategic Planning Teleconferences (SPT).

As convective weather continuously evolves, the achievable throughput for a region of en route airspace can fluctuate significantly over periods as short as 15-30 minutes. It has been operationally difficult to proactively identify the need for (and then implement) tactical adjustments to AFP throughput rates when these programs are in use. Without these adaptive AFP adjustments, inefficiencies in available airspace usage can arise, often resulting in increased air traffic delay.

Adaptive adjustments to AFPs are currently under investigation by the CDM Flow Evaluation Team (FET). However, the FET has not yet considered in detail the weather forecast information that would be needed for decision support for adaptive AFP adjustments. To this end, an en route airway blockage-based algorithm, using tactical forecast information from the Corridor Integrated Weather System (CIWS), has been developed in order to objectively estimate achievable flow rates through AFP boundaries during convective weather.

In this paper, we will analyze the characteristics of AFP usage in 2007 and 2008, focusing on the weather aspects of AFP parameter decision making process, in order to properly portray the potential advantages of an objective, tactical AFP throughput model. We will describe the route availability and traffic estimation model adapted to measure AFP throughput and present model results when applied to three weather impact events in 2006 and 2007. Recommendations for follow-on studies to refine and validate the weather-restricted flow-rate models, to progress from assessing (based on observed weather) to predicting (based on tactical weather forecasts) AFP throughput impacts, and to further assess concepts of integration into the Traffic Management process will also be discussed.

*This work was sponsored by the Federal Aviation Administration under Air Force Contract No. FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the United States Government.