CHICAGO – New air traffic control procedures are now in place at Chicago’s O’Hare International Airport to try to eliminate the risk of midair collisions over a pair of runways, after two near misses last year raised serious concerns, federal officials said Wednesday.

The planes involved in the incidents, which occurred three months apart in 2011, came within a few hundred feet of each other, according to a preliminary report released this week by the National Transportation Safety Board. No one was hurt, but the crew of one of the planes had to delay their takeoff and stay low to avoid a collision even though they were rapidly approaching the end of the runway.

Revised procedures put in place since last year include the extension of a warning system to automatically alert controllers if a plane is approaching to land on one of the runways as an aircraft is taking off on the other, the Federal Aviation Administration said Wednesday. The runways fall short of physically intersecting, but are close enough that air traffic can cross paths in takeoffs and landings.