A number of flights operated by LOT were grounded on Sunday after hackers attacked its computer system.
The attack targeted computers issuing flight plans at Warsaw’s Okecie airport.
More than 1,400 passengers were affected, with 10 flights cancelled and another 12 delayed.
Flights to Dusseldorf, Hamburg and Copenhagen and Polish cities were affected, although LOT stressed that the glitch did not affect the airport or aircraft that were already in the air.
The attack is being investigated by airline authorities.
“We’re using state-of-the-art computer systems, so this could potentially be a threat to others in the industry,” LOT spokesman Adrian Kubicki told the BBC.
The source of the hack is not yet known.