CHICAGO -- Federal transportation investigators released a preliminary report Monday about two near midair collisions at Chicago's O'Hare International Airport that raises questions about air-traffic control at one of the world's busiest airports.
The report released by the National Transportation Safety Board doesn't draw conclusions or assess blame for the incidents, which involved landing and departing planes coming within several hundred feet of each other. But it highlights concerns about the configuration of a control tower and two intersecting runways.
A final report isn't expected for several months.
Several controllers interviewed after a near miss on August 8, 2011, mentioned an obstruction in the middle of the air-traffic control room that forced controllers to yell vital information across the room. Others complained about potential confusion caused by the two intersecting runways.
The other near miss, which occurred on May 16, 2011, involved a SkyWest Airlines plane en route from Michigan approaching one runway and an ExpressJet Airlines taking off on the intersecting runway for Buffalo, N.Y. According to the report, the ExpressJet captain and others interviewed blamed at least one air-traffic controller for either forgetting or overlooking that the SkyWest plane had been given the OK to land.
The ExpressJet captain said his plane began roaring down a runway when he heard a distressed air traffic controller say, "Uhh!" Seconds later, the captain saw the landing SkyWest plane heading straight for his and frantically told his co-pilot to "stay low."
After the danger passed and he regained his composure, the captain radioed the tower after "nearly getting killed" and screamed at the air-traffic controller, "What the (expletive) was that?" according to the NTSB report.
The near miss happened shortly after Vice President Joe Biden's plane, Air Force Two, had touched down at O'Hare for a visit to Chicago. That plane wasn't directly involved, but others interviewed said the controller may have been distracted by the special procedures surrounding the arrival of Biden's plane, which include the presence of a helicopter.
The Aug. 8, 2011, incident was similar in that it involved a Chautauqua Airlines flight coming in from La Crosse, Wis., and a Trans State Airlines flight taking off for Moline, in western Illinois. Again, the landing plane nearly collided with a plane as it tried to take off.
The Trans State's pilot said he and his co-pilot spotted the incoming plane themselves as their plane was "running out of pavement" barreling down the runway. Had they not taken evasive action on their own by slightly delaying takeoff, the warning from the tower might "have been too late," according to the report.
The controllers, supervisors and others interviewed in that incident said the island-like obstruction in the center of the tower room might have been a factor, but the report didn't offer specifics about what the obstruction was or how it may have affected controllers' work that day. Though at least one air-traffic controller didn't believe it was a factor.
Asked by investigators why the room hadn't been reconfigured, one air-traffic controller cited "stubbornness" on the part of those who designed it. And a control supervisor said the configuration has "got to go."
A message left late Monday seeking comment from the NTSB was immediately returned.
Chicago Department of Aviation spokeswoman Karen Pride said she couldn't comment until airport officials had been able to review the report.
Chicago-based transportation expert Joseph Schwieterman said he hadn't seen the preliminary report, but he said air-traffic controllers over the years have expressed concern about some design features at O'Hare.
"My takeaway is that O'Hare – despite improvements over the years – still has a lot of older features that can create incidents," he said. "It is still a highly complicated airport – with intersections that are potential problem spots."
But while near misses always raise some concerns, he saw no reason why they should cause alarm among air travelers passing through O'Hare. He noted that such incidents are extremely rare, especially consideringthe volume of U.S. air passenger traffic.