A series of runway foul-ups at Denver International Airport over the past year - including two near-collisions - has forced a major overhaul of the airport's runway- and taxiway-safety program.
It also led the Federal Aviation Administration to send a high-level runway-safety team to DIA last month to review the airport's progress in making safety improvements.
The two near-collisions were among 24 serious runway incursions at U.S. airports - out of more than 61 million takeoffs and landings - in the year that ended Sept. 30.
DIA was the only U.S. airport to have two runway incursions in the government's most serious category, according to FAA data obtained by The Denver Post. The airport also had two less-serious incursions.
On Feb. 2, a DIA snowplow driver drove onto Runway 8-26 in front of a United Airlines jet that had just landed.
A collision was avoided only because the plane's pilots used emergency braking to slow down as the plow crossed in front of the plane.
The snowplow incursion came after the pilot of a small cargo plane on Jan. 5 missed a planned turn onto a taxiway and turned instead onto a runway just as a Frontier Airlines jet was about land.
The Frontier pilots aborted the landing to avoid hitting the cargo plane. The two aircraft came within 145 feet of each other, an FAA report said.
The agency ranked both DIA incidents as "Category A" incursions - the most serious - where "extreme action" is needed to narrowly avoid collision.
Category B incursions are those where "there is a significant potential for collision." Category A and B incidents are deemed "serious" by the FAA.
DIA and Los Angeles International were the only U.S. airports to have two serious incursions. Both of DIA's infractions were Category A incidents, and Los Angeles International's two incursions were Category B.
From 2003 through 2006, DIA did not have a single serious runway incursion.
The snowplow incident led airport officials to ask, "How could this possibly have happened?" said John Kinney, DIA's deputy manager for operations.
It led to a revamping of DIA's driver-training program for those who take vehicles onto the sprawling airfield - especially those with select access to taxiways and runways.
"It was an alarming event that necessitated we look at driver training from A to Z," Kinney said of the February incident, which prompted other safety improvements as well.
The airport added bold, colorful warning signs to intersections where roads for airport vehicles cross or enter taxiways and runways.
DIA is adding grooved rumble strips to the pavement at critical intersections as yet another warning device for drivers.
"This is a complex, intimidating airfield," Kinney said. "It's complex because of its sheer size, number of runways and taxiways" and many roads for emergency vehicles and those who maintain navigational aids.
There were also several less- serious incidents this year in which airport maintenance employees drove across active runways, DIA officials said.
In response to the flurry of incursions, DIA sharply reduced the number of people authorized to drive on the airport's "movement area" - the taxiways and runways - to 340 from 600.
Airport officials also mandated rigorous annual driver training.
The snowplow operator in the February incident was not badged to cross the taxiway and runway without an escort and ignored stop signs and warnings that he was about to enter an active runway, the National Transportation Safety Board said. The plow driver no longer works for DIA.
On a recent tour of DIA's airfield, Kinney acknowledged that some of the airport's warning signs were not large or prominent before the snowplow incident.
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