Atlanta Holding Case Study: Identifying a need for the Advancement of En Route Meteorology Programs

A case study was conducted on the commercial air traffic holding at the Atlanta Hartsfield- Jackson International (ATL) airport from 1 October 2002 through 30 September 2003. The purpose of the study was to quantify the effects Center Weather Service Units (CWSU's) have on traffic movement plans and programs that allow traffic flows within the National Airspace (NAS). During this process, several other findings became apparent, including the opportunity for a redefined CWSU forecast focus on “en route aviation meteorology”.

En route aviation meteorology differs from traditional aviation meteorology in that it shifts the focus from the pilot as the primary user, to the air traffic controller. This shift makes traditional terms, such as Visual Flight Rules (VFR), Marginal Visual Flight Rules (MVFR), Instrument Flight Rules (IFR), etc., obsolete in the air traffic management profession. The study identified that VFR, IFR and MVFR are not as important as the unique altitude criteria established for an individual airport's maximum traffic flow capability.

Airport traffic flow capability and maximum capability are unique to each major airport, and depending on the number of runways, their configuration, and customer demand. Maximum capability is the number of aircraft an airport can land and depart during a given time frame. What this study refers to as a “push time” is a period which the airports demand exceeds its maximum capability. This is a phenomenon that is common in most major airports in the United States, and is especially a problem at ATL. Weather effects become most critical to aircraft movement and safety during these push times.

Aircraft and passenger safety become a factor when aircraft are held (put in race track patterns which keeps them from advancing) at major airports and the airspace and altitudes designated for aircraft to hold becomes full. This makes the margin of error for an air traffic controller much smaller. The “big sky” theory has been used as a theoretical philosophy to cushion the fear that a near misses or aircraft collisions may occur, believing that the sky is so large and aircraft are so small that two will never occupy the same space. This theory becomes less acceptable during times of holding when more and more aircraft are placed in the same vicinity. Thus, there is a need to anticipate and alleviate weather-related holding at major airports. Not necessarily just during severe weather events, but during any weather condition that would restrict the ability of a large airport to land aircraft at a normal rate.