On Tuesday, two planes mistakenly cleared for takeoff on intersecting runways came within 100 feet of colliding with each other, the Chicago Tribune reported. On Thursday, a plane cleared for takeoff and another taxiing on an intersecting runway came within 600 feet of one another.
Greg Martin, a spokesman for the FAA in Washington, said incidents as serious as Tuesday's are "extremely rare" -- less than one in a million takeoffs.
"We have gone an entire year without having a serious incident like that at any U.S. airport," Martin said.
Both the recent near misses appear to have been caused by air traffic controller error.
The controller involved in the more serious incident was new to O'Hare and working under the supervision of another controller. A third person in the tower noticed the planes were on a collision course and ordered the pilots to brake.