What happened
On the afternoon of Sunday, 21 December 1997, a significant loss of separation occurred between two scheduled passenger flights operating within controlled airspace. A BAe 146 aircraft overtook a Fairchild Metro while both were traveling along the same flight track and at the same altitude. The encounter was characterized by extremely narrow margins, with the horizontal distance between the two aircraft estimated to be between 100 and 500 meters, and a vertical separation of only 20 to 150 feet.
The investigation
An investigation into the incident established that both aircraft were operating in accordance with their assigned air traffic control clearances. At the time of the encounter, both flights were under active radar monitoring. However, the investigation revealed that the radar controllers stationed in both Auckland and Christchurch failed to identify the developing conflict between the two aircraft.
Findings
The primary issue was the failure of air traffic controllers to perceive the proximity of the two aircraft despite both being under radar supervision. The investigation highlighted several critical vulnerabilities in the existing safety environment, including the inherent difficulty for flight crews to maintain constant situational awareness regarding surrounding traffic. Furthermore, the investigation noted limitations in how controllers utilized radar information and flight progress strips to monitor the airspace.