Crucial time was wasted in the air traffic control room at Chek Lap Kok airport despite early ground radar warnings of the possibility of a collision between Dragonair and SilkAir planes, a source has claimed.
The source, who claimed to have witnessed the incident on Saturday, said there was a scene of confusion as the radar controller and her supervisor watched the alerts flash up.
First a Proximity Conflict Alert (PCA) sounded. At this point, the radar controller or her supervisor could have issued a corrective instruction but did not, the source said.
The controller's supervisor stood behind her monitoring the planes on the screen but nothing was done until after a more serious alert - a Conflict Alert (CA) - was activated.
'Based on the projection of the flight path of these two flights, they would meet exactly at a point.
'The traffic controller was not aware of this,' the source claimed in a written statement, which then described a scene of confusion.
'As no recovery action was taken, the two planes flew closer and closer. Ten seconds after the PCA warning, the warning changed to CA.
'The two planes were less than 10 nautical miles apart and getting closer. Recovery action . . . must be prompt, clear and precise at this dead stage.' The source claimed nothing was done until after the Dragonair pilot had begun to take action himself.
The pilot steered right to avoid a mid-air collision after his inflight radar, described in manuals as the last line of defence, sounded a crash warning.
Last night, the Civil Aviation Department insisted the radar controller did instruct the pilot to turn before the pilot began the manoeuvre.
But a department spokeswoman admitted the instruction was only 'a very short time' before the on-board radar sounded an alert.