The i-PreChecking (IPC) system went offline at around 6:05 a.m., preventing airlines nationwide that rely on it from processing passengers at their check-in counters, Korea Joongang Daily reported.

About 15 minutes later, the airport's immigration office instructed airlines to issue boarding passes manually.

The system resumed operation at approximately 7:25 a.m., 80 minutes after the disruption began.

Manual processing caused congestion, delaying nine flights operated by six airlines.

Passengers at Incheon International Airport in South Korea. Photo by Reuters

The IPC connects the Justice Ministry's immigration database with airlines' reservation and ticketing systems, allowing passenger information to be screened in real time before boarding passes are issued, The Chosun Daily reported.

It checks travelers against databases of international terrorists, individuals prohibited from entering South Korea and holders of lost passports to prevent high-risk passengers from boarding flights.

The ministry is investigating the precise cause of the outage but suspects it may have been linked to work replacing aging storage equipment in its border management system.

Incheon ranked Asia's second best airport after Singapore Changi in the 2026 Skytrax World Airport Awards. It handled 38.39 million international passengers in the first half of this year, a 6.3% increase from the same period last year.

The Korean airport saw the strongest growth among the top 10 international airports in terms of scheduled seat capacity in October, according to British aviation firm OAG.

The incident came just four days after a separate check-in disruption at the airport that delayed 35 flights and stranded 1,200 passengers.

October and November are typically peak tourism months in South Korea, as tourists flock to see the country's autumn foliage.