Description

On 16 August 2007, a Boeing 737-700 being operated by Westjet on a scheduled passenger flight from Calgary to Los Angeles and taxiing in at destination after landing on runway 24R began to cross runway 24L on which an Airbus A320 being operated by Northwest Airlines was taking off in normal day visibility. It stopped after being instructed to by ATC but the right wing of the departing A320 passed close to the nose of the 737.

Investigation

An Investigation was carried out by the National Transportation Safety Board (USA) (NTSB). It was found that at the time of the incident, both northern runways were in use for landings and runway 24L also for take offs. The prevailing ground visibility was normal.

It was established that the 737 had exited runway 24R by means of a hard left turn onto taxiway ‘Y’ and had then changed to GND frequency without any such instruction being given. The phraseology used by the 737 flight crew when checking in with GND led the controller to initially assume that the TWR controller had already cleared the aircraft to cross runway 24R and so had responded with a confirmation to continue taxiing to the already-identified gate. Ten seconds later, as the 737 approached runway 24R, its crew called GND for confirmation that they were cleared to cross. Initially, the aircraft identification was missed by the GND controller but when he asked who called and the request for confirmation was repeated, he realised that the aircraft had not been given permission to cross and told it to stop. He subsequently advised that he had not initially realised that the 737 still had to cross runway 24L to reach the terminal area.