Two passenger flights carrying more than 600 people came within seconds of a head-on collision over Hong Kong International Airport this month, an investigation by The Standard reveals.
Both pilots had to activate the collision avoidance system - with one climbing and the other descending - 17 seconds after they allegedly did not respond to instructions from the air traffic control center.
The Cathay Pacific Boeing 777 and Dragonair Airbus A330 had 613 passengers and crew aboard.
Former civil aviation chief Albert Lam Kwong-yu estimated the flights were about six seconds from crashing, judging from the distance between them and the normal speed of aircraft. "The chance of a crash is absolutely high," he said. "The passengers really came back from hell."
But a Cathay Pacific spokesman insisted: "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 apart when abeam from each other with increasing vertical separation."
At about 1pm on September 18, Cathay Pacific flight CX841, returning from New York with only 10 minutes of holding fuel, requested permission to land. Five other aircraft were waiting to land at that time, including Dragonair flight KA433 returning from Kaoshiung, Taiwan.
Another flight, KA330, was circling at 22,000 feet, while the other aircraft were at lower levels. They were about 66 kilometers southwest of the airport, flying in poor weather.
According to the Civil Aviation Department, another Cathay Pacific flight offered to swap its landing slot with the CX841 Boeing, but the controller detected "a conflict" between CX841 and KA433. They were getting so close at the same altitude that they were already in visual contact.
Sensing the danger, the department said, the controller immediately ordered the KA433 Airbus to turn, but the crew "did not accept the instructions."
The controller then instructed CX841 to climb for vertical separation to avoid collision, but it received no response.
About 17 seconds later, KA433 activated "TCAS climb" - or traffic collision avoidance system. CX841 also activated "TCAS descent," according to the department.
They passed each other at a distance of one nautical mile, or about two kilometers. The department said: "The avoiding actions were executed in a controlled manner and as both pilots had the other aircraft in sight well in advance, there was no risk of collision."
There were 18 crew members and 299 passengers aboard the Cathay Pacific Boeing and 12 crew and 284 passengers aboard the Dragonair Airbus.
Lam said he never saw such a dangerous and serious situation during the six years he served as chief of the department. He called for the establishment of an independent panel to probe the incident.
"Are the staff [at the control center] overloaded with work? Have they received enough training? Are they sufficiently experienced?
"There are many questions behind this incident. Someone must accept responsibility."
A Cathay Pacific spokesman said there was never any danger. He stressed that the aircraft's TCAS equipment generated appropriate alerts.
He also said the aircraft was left with 50 minutes of fuel after it landed.
However, the Civil Aviation Department said the standard horizontal distance between two aircraft is five nautical miles, or around nine kilometers. It is conducting an investigation with the help of both Cathay Pacific and Dragonair.
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