Operational error by an air traffic controller caused an ExpressJet Embraer ERJ-145 to pass only 300ft in front of a light aircraft as the two departed on intersecting flightpaths last June, US investigators have found.

The Cessna 172 had been cleared for take-off from Runway 18 at Gulfport-Biloxi airport, Mississippi by the tower controller. Sixteen seconds later, the ERJ-145 stated it was ready for departure from Runway 14, and the same controller cleared it for take-off. While the runways do not intersect, their flightpaths do. "While both airplanes were about 300 feet [90m] above the airfield, the Embraer passed in front of the Cessna," said the National Transportation Safety Board. It added that the aircraft were separated by 300ft horizontally, but not separated vertically, at their closest point.

During an interview the lead controller said from previous experience he thought the Cessna would take 3-5min to become airborne, enabling the ERJ to depart well before. When the ERJ queried him about the Cessna, he did not understand how the two aircraft could have conflicted with each other, and assumed the ­Cess-na was a no-radio arrival on a go-around.

Traffic information about the converging flightpaths was not issued to either aircraft. The event "revealed a number of deficiencies" at the air traffic control facility, the NTSB added.

Source: Air Transport Intelligence news