Errors that allowed planes to get too close in U.S. airspace rose 32 percent last year, according to preliminary numbers released during a Senate hearing today.
The incidents that were considered the nearest misses increased fivefold, from 55 in 2011 to an estimated 275 last year, according to written testimony by Jeffrey Guzzetti, assistant Transportation Department inspector general. The number of close calls on runways also rose last year, according to Guzzetti.
It’s not clear if the numbers show increased risk because the Federal Aviation Administration last year broadened its definition of such incidents and began more automated error detection and reporting, actions that may have raised the reported figures, according to Guzzetti.
“The reason these increases occurred is unknown,” Guzzetti wrote in a report prepared for the Senate Commerce, Science and Transportation Committee hearing.
The FAA said the higher numbers stem from its efforts to increase reporting and don’t reflect more incidents, according to Guzzetti’s testimony.
The U.S. rules on how far apart planes vary. As they arrive and depart from airports, they must usually stay separated by at least three nautical miles (5.5 kilometers) or by 1,000 feet (305 meters) of altitude.
A runway incident occurs when a plane, vehicle or animal enters a runway occupied by an aircraft.
The FAA in recent years has developed new programs to encourage air-traffic controllers to report errors and has improved computerized systems to better track such cases.
There was a 54 percent boost in such incidents from 2009 to 2011, according to FAA data.
Runway incidents that came closest to a collision rose from seven in 2011 to 18 last year, as the number of flights decreased 1 percent, Guzzetti said.
Incidents in which aircraft flew closer than allowed under federal regulations increased from 1,895 in 2011 to 2,509 in the year that ended last Sept. 30, according to the testimony. Planes in most of those incidents were in little or no danger of colliding.
Starting last year, the FAA began tracking all cases in which planes came too close together. Previously, its count included only those in which a controller’s error had caused such incidents, according to Guzzetti.
The FAA needs to do a better job of collecting data on such incidents, Guzzetti said. In some cases, incidents are reported anonymously under an FAA program and aren’t included in error totals, he said.
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