JAL said the problem started Thursday morning when the company's network connecting internal and external systems began malfunctioning.

The airline said it was able to identify the cause as an attack intended to overwhelm the network system with massive transmissions of data. Such attacks flood a system or network with traffic until the target cannot respond or crashes.

The attack did not involve a virus or cause any customer data leaks, JAL said. It said that as of late morning, the cyberattack had delayed 24 domestic flights for more than 30 minutes.