Tokyo. Japan Airlines (JAL) faced a cyberattack on Thursday, disrupting its network and causing delays to more than 20 domestic flights during the busy year-end holiday season. The airline reported that it managed to stop the attack and restore its systems within hours, ensuring no impact on flight safety.

The issue began Thursday morning when JAL's network, which connects internal and external systems, malfunctioned. The airline later identified the cause as a distributed denial-of-service (DDoS) attack, which floods a network with massive amounts of data to overwhelm it. JAL confirmed that the attack did not involve a virus or result in any customer data breaches.

As of late morning, 24 domestic flights experienced delays of more than 30 minutes. Ticket sales for both domestic and international flights were temporarily suspended but resumed later in the day.

Experts have repeatedly raised concerns about the vulnerability of Japan's cybersecurity, especially as the country steps up its defense capabilities and works more closely with the United States and other partners with much tighter cyber defenses. Japan has taken steps, but experts say more work is needed.

In June, Japan's space agency said it had suffered a series of cyberattacks since 2023, though sensitive information related to rockets, satellites, and defense was unaffected. It was investigating to take preventive measures. Last year, a cyberattack paralyzed operations at a container terminal at a port in the city of Nagoya for three days.

JAL's ticket sales for both domestic and international flights scheduled for departure on Thursday were suspended temporarily but resumed several hours later.

Chief Cabinet Secretary Yoshimasa Hayashi told a regular news conference Thursday that the transport ministry told JAL to hasten efforts to restore the system and to accommodate affected passengers.

Other Japanese airlines, including ANA Holdings, Skymark, and Starflyer, were not affected.

Television footage showed many passengers at Tokyo's Haneda airport crowded into its terminals as the attack hit the year-end holiday travel season. Offices will close from this weekend for the New Year holidays, the biggest celebration of the year, when millions of people travel back to their hometowns from the cities.