A former Korean Air executive whose on-board "nut rage" tantrum delayed a flight has been freed from prison after a South Korean court suspended her jail term.

Cho Hyun-ah, the daughter of the airline's chairman, did not break aviation security law when she ordered the chief flight attendant off a December 5 flight, forcing it to return to the gate at John F Kennedy Airport in New York, Seoul High Court ruled.

But the upper court said she was guilty of using violence against flight attendants and sentenced her to 10 months in prison, suspended for two years. A lower court previously sentenced her to a year in jail.

Cho achieved worldwide notoriety for her tantrum, triggered when a first-class flight attendant served her macadamia nuts in a bag instead of on a dish. Cho, head of the airline's cabin service at the time, had a heated, physical confrontation with members of the crew.

Mobbed by reporters at the court, she made no comment in front of the TV cameras, bowing her head and burying her face in her hands as the media pressed in, yelling for her to say something.

The incident was a lightning rod for anger in a country where the economy is dominated by family-run conglomerates known as chaebol, that often act above the law.

Cho was previously convicted of forcing the flight to change its route, obstructing the flight's captain in the performance of his duties, forcing a crew member off a plane and assaulting a crew member. It found her not guilty of interfering with a transport ministry investigation into the incident. Cho pleaded not guilty and prosecutors had called for three years in prison.

The aviation security law was enforced to regulate highly dangerous acts such as hijacking the plane. But the high court ruled that Cho's actions did not pose a big safety threat and returning the plane that was taxiing did not constitute forcing a change in its route.

Kim Sang-hwan, head of the three-judge upper court panel, said even though Cho committed the crime of using violence on crew members, she should be given a second chance. The judge also cited her "internal change" since she began serving her prison term as a reason for lessening the sentence.

The court also took into consideration that Cho is the mother of two-year-old twins and had never committed an offence before. She has resigned from her position at the airline.

"It appears that she will have to live under a heavy criticism from the society and stigma," said Judge Kim.

Cho's release did not go down well with some people.

"If she was released because she showed repentance, other criminals should be equally released," said 19-year-old college student Kim Ryeong-hui.

"I think the court went easy on her. I feel angry when people mistreat other people in lower ranks."