While the Federal Aviation Administration acknowledges that flight delays originating in the New York metropolitan area propagate nationwide, the agency is unable to say how large that ripple effect is.

The Transportation Department inspector general, in a report dated Oct. 28, says FAA's inability to accurately characterize how late New York flights propagate delays in the national airspace system stems in part from bad databases.

The New York region is one of the most congested and delayed aviation areas in the nation, with more than 1,900 aircraft passing through Kennedy, LaGuardia and Newark airports on a typical summer day, a quarter of aircraft going through more than once, the report notes.

A combination of airport capacity, continued growth and crowded airspace have conspired to increase the number of delayed flights by 46 percent over the past decade in the New York metropolitan area, the report adds.

Yet, no one fully understands how or to what degree New York delays impact flights nationwide even as there is widespread agreement that they do, the report says.

According to the inspector general, the FAA draws on two databases to track delays, and neither provides all the necessary data to fully measure delay propagation.

One database, maintained by the FAA itself, tracks the tail numbers of only 40 percent of U.S. aircraft. Another database, maintained by the Bureau of Transportation Statistics, contains tail numbers from the 19 largest U.S. domestic airlines, but that amounts to just two thirds of the flights that could be analyzed. The inspector general also says the BTS database has inaccuracies, although BTS officials told auditors they hope recently implemented validation controls will prevent errors from creeping in.

Other factors hindering a clear picture of flight delay propagation include the sheer complexity of the national airspace system and insufficient leadership and coordination by the FAA, the report states.

The agency does have underway two projects to study propagation effects--one undertaken by Mitre under contract--but both suffer from an assumption that an initial flight delay cause will be the cause of all subsequent flight delays. That's not the case, according to the report, since a flight could be initially delayed by a mechanical problem and on a subsequent leg be delayed by weather.

Unless the FAA comes up with a way to understand delay propagation, it will continue to miss opportunities to improve air traffic management and make better investment decisions, auditors warn.

The official agency response, signed by Clay Foushee, FAA director of audit and evaluation, says the FAA is evaluating the feasibility of collecting the tail numbers of U.S. air carrier international flights. As for auditors' criticisms of its delay propagation models, Foushee wrote that auditors "could better recognize the efforts FAA has pursued in this regard and the progress achieved."

For more:
- download the report, AV-2011-007 (.pdf)

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