Korean Air, South Korea’s No. 1 air carrier, apologized over the flight delay and inconvenience caused by Hanjin Group heiress Heather Cho amid the launch of a goverment probe.

“We apologize for the inconvenience caused to the passengers, and for turning the plane around despite it not being an emergency situation,” the carrier said in a statement released late Monday night.

The carrier maintained that a flight manager had neglected his duties by not being aware of whether or not it was suitable to serve nuts to passengers without asking them first.

On Monday, Cho, who is currently executive vice president of Korean Air run by Hanjin, forced the chief flight attendant to deplane after he failed to locate guidelines in the service manual about serving nuts.

The executive vice president had been sitting in the first-class section when she was served a bag of macadamia nuts by a junior flight attendant who failed to ask her if she wanted them. She also reportedly complained about the nuts not being served on a plate.

The plane, carrying some 250 passengers onboard and bound for Incheon from New York’s JFK Airport, went back to the terminal to drop off the flight manager.

Sensing the growing national uproar over the issue, the Ministry of Land, Infrastructure and Transport has launched an investigation into possible illegal misconduct on Cho’s part.

“The ministry plans to take measures such as reporting the case to judicial authorities if it is suspected that (Cho) violated related aviation laws,” said Lee Chang-hee, director of the Transport Ministry’s Aviation Security Division, adding that officials of the ministry’s aviation security and safety divisions are jointly investigating.

On Tuesday, Korean Air’s labor union released a statement calling for the company’s management to take responsibility for the nut incident, and not the deplaned flight attendant.

“The company is shifting its responsibility onto flight staff to conceal Cho’s flaws,” the union said in the statement.

Cho herself has yet to issue a formal apology, nor does she have plans to do so for the time being, according to those close to the matter.

By Park Han-na (hnpark@heraldcorp.com)