Passengers were advised to postpone non-essential travel and expect delays, as they would be redirected to manual lanes for immigration clearance. By 4pm the same day, automated immigration clearance at all checkpoints were back up and running. ICA said in a statement late-Thursday that preliminary investigations revealed a “technical glitch” had occurred during a pre-scheduled system upgrade, causing an “unanticipated system overload”. This brought down the automated immigration clearance systems, which affected all departure terminals at Changi Airport and arrival terminals at Terminals 2 and 4. ICA did not provide details on the system upgrade or whether the procedure was tested before the scheduled live rollout.
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