Air traffic controllers made more mistakes recently at Minneapolis-St. Paul International Airport than at five of the 10 American airports that had more plane traffic. And MSP had almost as many errors as the Atlanta airport, which is the nation's busiest with nearly three times the passengers.
The reasons are unclear, but the numbers may reflect a physical reality. Unlike some larger and newer airports, MSP's layout and its use of two major runways can increase the complexity of controlling takeoffs and landings. Hemmed in by freeways, homes and a national cemetery, it lacks the space some other airports have for more runways.
"It's just a different steer to wrangle," said Sam Tomlin, a veteran air traffic controller at MSP. "There's a lot of stuff going on."
Controller mistakes typically involve planes getting too close to each other. Seventeen errors occurred at MSP from late 2010 to early 2012, the most recent period for which such data are available. They are included in reports, covering hundreds of airports, that were released by the Federal Aviation Administration in response to a Freedom of Information Act request by the Star Tribune. The FAA has since changed its method of classifying problems, but has not released those records.
The errors at MSP happened at a faster pace than previously. From late 2006 through late 2010, there were a total of 21 errors.
The FAA acknowledges that intersecting or converging runways at MSP can create complications and opportunities for errors.
"Every time you have an intersection, you have an opportunity for conflict," said FAA spokeswoman Laura Brown. "It doesn't mean that you can't operate safely." She said comparing traffic control at airports is difficult and that "each airport has its own set of challenges."
Nationwide, tower errors increased 82 percent over five years. While the FAA has attributed much of the spike to better reporting, the Office of the Inspector General for the U.S. Department of Transportation this year stressed problems.