South Korean prosecutors on Thursday launched a probe into allegations that Korean Air's CEO and his sister are responsible for a former executive's taking payments from Airbus in return for buying that company's aircraft.

This year, Airbus said it would pay a record $4 billion in fines after reaching a plea bargain with prosecutors in Britain, France and United States over accusations of bribery and corruption stretching back at least 15 years.

A French document detailing Airbus' settlement said Airbus had agreed to pay €15 million ($1.07 million) to a former top Korean Air executive in return for the airline's purchase of 10 A330 jets under contracts dating from 1996 to 2000, then delivered part of the cash through a fake consulting contract using a middleman.