An investigation was launched after a Cathay Pacific plane and a Dragonair jet carrying more than 600 passengers and crew between them had to take evasive action when they strayed into each other's path as they flew into Hong Kong.
Collision warning alarms sounded in the cockpits of the Cathay Pacific flight from New York with 299 passengers and 18 crew members on board, and the Dragonair flight from Kaohsiung, Taiwan, carrying 284 passengers and 12 crew as both planes approached Chek Lap Kok on September 18.
The two planes came within 2,000 metres of each other. They headed towards each other as they circled the airport amid congested airspace caused by bad weather, which led to several flights being diverted.
Traffic collision avoidance system (TCAS) alarms went off in the cockpits of both planes and the pilot of the Cathay Pacific flight descended while the pilot of the Dragonair flight climbed to put a safe distance between the two aircraft.
An air traffic controller said the airspace over Hong Kong was so congested at the time of the incident that the Dragonair flight then came too close to another plane waiting to land and had to change direction for a second time. The airlines, however, say there was only one incident. A spokeswoman for both Cathay Pacific and Dragonair yesterday confirmed the initial incident and said the matter had been reported to the Civil Aviation Department for an investigation.
During the same period, she said, eight other Cathay Pacific aircraft had to divert to Taipei, Kaohsiung, Macau and Guangzhou while a Cathay Pacific flight from London was kept in a holding pattern for so long that it made an emergency landing request.
The incidents come amid record numbers of inbound and outbound flights from Hong Kong and complaints from air traffic controllers that staff members are under increasing strain to cope with a rising workload.
The Cathay Pacific spokeswoman said in a statement that there had been a 'loss of separation' between the Cathay Boeing 777-300ER flight CX 841 from New York and Dragonair Airbus A330 flight KA433 from Kaohsiung at 1.13pm on September 18.
'The CX841 and KA433 aircraft were at the same altitude southwest of HKIA [Hong Kong International Airport] when a loss of separation resulted,' she said. 'The pilots of the two aircraft properly responded to their respective traffic collision avoidance system warnings and advisories, with KA433 climbing and CX841 descending immediately to resolve the conflict and maintain appropriate separation.'
Both planes landed safely, the Cathay Pacific flight touching down at 1.45pm and the Dragonair flight 14 minutes later.
The spokeswoman said: 'There was no risk of collision and at no time was the safety of the flights compromised. At the closest, they were one nautical mile [1,852 metres] apart when abeam from each other with increasing vertical separation.'
One air traffic controller said: 'Although the weather was a contributing factor, the whole situation illustrated there was no contingency plan, no backup and supervisors responsible for a general overview of traffic were covering traffic positions. Once again the staffing situation is glaringly obvious.
'When the Dragonair plane turned away it was involved in a breakdown separation with a third aircraft.
'The controllers on duty described it afterwards as a near-collapse of the air traffic control system.'
The air traffic controller said about 40 controllers had been assigned to a project connected to the new air traffic control centre at Chek Lap Kok.
Meanwhile, he said, traffic levels had exploded. 'It's not unusual to have in excess of 200 aircraft parked on the airfield at 7am any morning. Surely this is a serious indication of the traffic levels that we are now dealing with,' the controller said.
A Civil Aviation Department spokeswoman yesterday confirmed the incident. She said the controller on the ground had taken appropriate corrective action 'in a calm and timely matter'.
The department is conducting an investigation.