The sun is shining, skies are clear, and you remember seeing a weather map free of storms. Yet your flight sits on the taxiway for what seems to be a long time, queued for takeoff. A recent study completed for the Federal Aviation Administration (FAA) suggests that your delay is likely caused by another flight's missed departure or arrival.

A missed departure occurs when an aircraft enters a runway to take off, but instead exits the runway without departing because of a mechanical or other issue. A missed arrival happens when an aircraft begins its final approach to land, but exits the approach path without landing, which could be a result of unexpected weather or traffic on the runway. Missed departures and arrival maneuvers, either of which can result from unexpected weather or traffic encroaching in a runway, must be managed with regard for passenger safety.

Because of the safety concerns, the FAA Office of Accident Investigation and Prevention's Dr. Sherry Borener and Larry Berk and Ruth Hunter from Volpe's Center for Safety Management Systems, along with Boeing, and Saab Sensis studied delays at New York's John F. Kennedy (JFK) International Airport attributable to missed departures and arrivals. This study was undertaken as part of System Safety Management Transformation (SSMT), an FAA effort to predict impacts to aviation safety risks as enhanced technology and operational alternatives roll out under a transformation of the airspace called NextGen. NextGen is being implemented to safely increase the future capacity, efficiency, and flexibility of the National Airspace System (NAS), as air traffic is projected to double in the next 20 years.

The SSMT team conducted its study applying sophisticated computer simulation models to JFK airport flight data and ASDE-X surveillance data. ASDE-X, or Airport Surface Detection Equipment, Model X, a NextGen system improvement, provides detailed information about the location, identification, and movement of aircraft and ground vehicles (e.g., fuel trucks and baggage carts) on the airport surface and aircraft flying within 5 miles of the airport.

The study examined JFK traffic data spanning different times of year and estimated how frequently missed departures and arrivals occur. The findings suggest the following:

One missed departure can delay 16 other flights on average by nearly 4 minutes each under clear weather conditions. There is an 11 percent chance of a flight experiencing a delay greater than 15 minutes.
A missed arrival can delay 10 other flights by 2 minutes each on average, with the very low probability (0.3 percent) of a flight experiencing more than a 15-minute delay.

Follow-on analyses supporting SSMT and NextGen decision-making will assess effects at other airports on passengers and the local environment from traffic delays under differing weather conditions.

The results from such simulations serve as baseline performance data for safety analyses. These data help the FAA ensure that NextGen will maintain the high operational safety level of the world's safest air transportation system. "The NextGen conventional wisdom is that an automated National Airspace System will be safer and more efficient." said Berk. " The Volpe Center has been given a tremendous opportunity to partner with FAA in studying that premise."

Volpe staff members in the Center for Safety Management Systems are helping to provide the FAA with the data and techniques to evaluate NAS throughput, safety risk, passenger impacts, and fuel burn/environmental effects. This research is conducted in collaboration with staff in the Center for Environmental and Energy Systems and the Center for Human Factors Research and System Applications. In addition, Volpe's Center for Air Traffic Systems and Operations staff is assisting with the planning, research, testing, and evaluation activities in support of NextGen.

This work will be presented at the 31st Digital Avionics Systems Conference, October 14-18, 2012 in Williamsburg, VA.