The back-up flight data system was not used on airport opening day because it may have also failed, it was revealed yesterday.
The Airport Authority admitted the reserve system may have caused a second wave of problems if it stalled like the main flight information display system at Chek Lap Kok on July 6.
The Commission of Inquiry on the New Airport heard such a scenario could have worsened the opening which was already thrown into chaos when the main system came to a near standstill.
Airport management director Chern Heed told the commission it was better to re-boot the ailing main system rather than risk a more 'severe' situation by switching over to the standby.
He said it was better to 'persist' with solving faults with the main system and get it back up to speed.
'The main problem was the slowness and the best way out was to re-boot it. We felt if we were going to work out this problem, we should persist and see it through so we could eradicate it,' Mr Heed said.