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21 passengers missed flights at Changi Airport Terminal 4 during immigration clearance disruption in March

ICA is in the process of implementing a multi-year plan where all manual counters and automated lanes will be replaced in phases with next generation Automated Border Clearance System gates.

21 passengers missed flights at Changi Airport Terminal 4 during immigration clearance disruption in March

In a photo taken at 1.40pm, passengers are seen queuing up at the immigration area in Changi Airport's Terminal 3 on Mar 31, 2023. (Photo: CNA)

SINGAPORE: A total of 21 passengers missed their flights at Changi Airport Terminal 4 as a result of the immigration clearance disruption on Mar 31, Minister of State for Home Affairs Muhammad Faishal Ibrahim said in parliament on Friday (Apr 21).

He was responding to questions from Members of Parliament on the disruption which caused delays and snaking queues at Singapore's checkpoints.

About 30,000 passengers on 113 departure flights and 111 arrival flights cleared immigration during the disruption, said Assoc Prof Faishal.

The 21 passengers who missed their flights at Terminal 4 after clearing immigration were subsequently offered rebookings on alternative flights within a week at no extra cost, he added.

Among them, 11 rebooked their flights and departed on the same day, while four passengers flew the next day, the Ministry of Home Affairs clarified after Assoc Prof Faishal's speech.

Four passengers departed by land, while the remaining two stayed in Singapore.

At Singapore's land checkpoints, travellers experienced delays of up to 30 minutes at the onset of the incident, said Assoc Prof Faishal. But at Woodlands Checkpoint, there was later another hour of delay for cars as the car arrival zone had to be converted to clear motorbikes manually, he added.

About 55,000 travellers passed through the two land checkpoints during the disruption.


The disruption was a result of a "severe system overload" after a pre-scheduled trial for an upgrade of the Multi-Modal Biometrics System (MMBS), said Assoc Prof Faishal. The trial was conducted at about 10.40am on Mar 31.

The MMBS facilitates automated immigration clearance using travellers’ biometrics.

As a result, automated clearance lanes at all the departure halls in Changi Airport and certain automated lanes at Woodlands and Tuas Checkpoints were affected. The rest of the automated lanes, including those at the sea checkpoints, remained operational.

"Prior to the incident, ICA had been upgrading its systems progressively and cautiously, with 10 out of 12 systems enhanced. Only the MMBS and one other system had not yet been upgraded," said Assoc Prof Faishal.

"For the MMBS, the system upgrade would involve replicating the large biometric database to an upgraded system. This has to be done continuously over a few days, and the MMBS has to remain operational during this period."

As per standard procedure for any system upgrade, tests in the User Acceptance Test environment were conducted beforehand, said Assoc Prof Faishal. These tests were successful and subsequent trials in the production environment were also stable.

"Next, we had planned to conduct further controlled trials during different times of the day, to ascertain that the system upgrade would not disrupt operations during the wee hours, off-peak hours, and peak hours, before proceeding with the actual upgrade," he added.

The "wee hours" trial was conducted on Mar 15 from 1.30am to 3.30am, and was successful.

"The trial on 31 March 2023, when the incident happened, was the off-peak hours trial, to take place from 10am to 2pm. The vendors were on standby on-site, and the plan was to recover the system within 30 minutes if the trial did not go well," he explained.

"The trial caused the storage systems to overload at about 10.40am, and the process was aborted immediately. However, the extent of the overload was much more severe than anticipated, and the vendors who were on-site had to work with their global support team to diagnose and reboot the servers."

The recovery process ultimately took about four-and-a-half hours and the MMBS recovered around 3pm.

ICA immediately activated its Business Continuity Plan once the system went down, said Assoc Prof Faishal. This meant that off-duty officers were recalled to help man manual immigration counters and perform crowd control.

"Across all the checkpoints, the failover process kicked in, and all the manual counters, and certain automated lanes, switched to backup systems. Not all the automated lanes have this failover capability, as different models were procured over the years," he added.

"Travellers were redirected to manual counters for immigration clearance. ICA immediately stepped-up manning of the manual counters through a combination of measures such as recalling off-duty officers, deploying administrative staff and retaining the officers from the outgoing shift." 

In addition, Changi Airport Group (CAG) assisted ICA by deploying additional Changi Youth Ambassadors and office staff, along with CAG’s duty terminal managers and their Customs, Immigration and Quarantine Team.

These individuals helped identify travellers whose flights were departing soon so that their departure clearance could be prioritised. Public announcements were also made to appeal for such travellers to step forward.


ICA is reviewing the approach to the upgrade in light of the incident, said Assoc Prof Faishal.

"We apologise to affected travellers for the inconvenience caused and thank them for their understanding. I would also like to thank the ICA officers and CAG staff who had worked tirelessly, without complaint, to deal with the situation," he said.

Moving forward, ICA is in the process of implementing a multi-year plan, known as the New Clearance Concept (NCC), to transform immigration clearance across all the checkpoints, Assoc Prof Faishal said.

Under the NCC, all manual counters and automated lanes will be replaced in phases with the next generation Automated Border Clearance System (ABCS) gates, which will allow travellers to continue using automated clearance even when the MMBS is down.

In the meantime, the resiliency of existing automated lanes that have yet to be replaced by the ABCS gates will also be enhanced in the second half of 2023.

"Singapore is one of the first countries in the world to implement NCC-type capabilities. Some of these capabilities will be implemented in a form and manner not used or tested elsewhere, as we customise them to suit our operational needs," he added.

"As such, while we will work closely with all stakeholders to further minimise technical disruptions, and enhance system resiliency, the reality is, disruptions will still happen now and then. When they do, we will make sure we have robust contingency plans in place, and try to recover as fast as possible."

Source: CNA/mt(gr)


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