Almost 1,500 passengers scheduled to fly with Polish state-owned airline LOT had their flights canceled after unknown hackers attacked the airline’s computers.

“This is the first attack of its kind,” LOT spokesman Adrian Kubicki said.

Ten flights were grounded at Warsaw’s Frederic Chopin Airport around 4:00 p.m. local time, and by 9:00 p.m., LOT had fixed the problems caused by the hackers, and regularly scheduled flights were running again. LOT provided hotel rooms for passengers who had to stay overnight to wait for other flights.

Apparently, the hackers attacked the airline’s ground computer systems, making it impossible to issue flight plans.

LOT has been very clear that at no point during the hacking was anyone’s life in danger, and that the Chopin airport itself was not affected.

The airline’s planes were not affected, and planes already in flight prior to the 4:00 attack were able to continue without emergency landings.

“Aircraft that are already airborne will continue their flights. Planes with flight plans already filed will return to Warsaw normally,” LOT said in a press statement.

“We’re using state-of-the-art computer systems, so this could potentially be a threat to others in the industry,” Kubicki also said.

Polish authorities are investigating the hack, but they have not announced who they believe may be behind this attack.

In addition to the culprits, the intent of the attack seems unclear.

“In order to properly assess the impact and the target of the attack, we still need more information,” aviation cyber-security expert Ruben Santamarta told media.

Because the aviation industry relies so heavily on computers, airlines and airports take cyber-attacks very seriously.

Last year, five major international civil aviation organizations agreed to draft a “common roadmap” for dealing with cyber-threats and sharing information about hackers and cyber-security techniques across the industry.

“As technologies rapidly evolve and become more readily accessible to all, cyber-threats cannot be ignored,” International Civil Aviation Organization Secretary General Raymond Benjamin said at the December meeting in Montreal.

“This is an important new area of aviation security concern, and our global community will ensure that it is met with a strong level of commitment and response,” Benjamin also said.