SEOUL (AFP/KOREA HERALD/ASIA NEWS NETWORK) - The daughter of Korean Air's chairman was found guilty on Thursday of violating aviation safety law and sentenced to a one-year jail term, in a now notorious on-board "nut rage" incident that triggered an uproar over the behaviour of South Korea's elite business families.

Heather Cho, who was a Korean Air executive vice-president at the time, is also charged with obstructing justice and assaulting a member of the cabin crew. Prosecutors had demanded a three-year jail term.

The charges all stem from an incident in which Cho forced the chief purser off a Dec 5 New York-Seoul KAL flight, forcing the taxiing plane to return to the gate so he could disembark.

The 40-year-old had taken exception to being served macadamia nuts she had not asked for - and in a bag, not a bowl.

The district court in Seoul ruled that Cho had illegally altered the course of the plane, judging that an aircraft was "in flight" from the moment it begins to move.

As the primary issue over the past two months, the Seoul Seobu District Court also acknowledged in its ruling the charges raised by the prosecution that Cho violated the law, which bans passengers from pressuring crew members to deviate from the flight route.

Its verdict clarified that Cho should be held accountable for obstructing aviation safety in abuse of her authority.

In addition, the ruling reflected the charges that Cho physically and verbally assaulted a female flight attendant as well as the cabin crew chief.

In passing sentence, the judge indicated that Cho had failed to show enough remorse for her actions, even though she had submitted some letters to the court expressing repentance for her behaviour.

Cho had treated the flight "as if it was her own private plane", Justice Oh Sung Woo said.

"It is doubtful that the way the nuts were served was so wrong," the judge added.

The case triggered a huge public backlash.

Cho, who has been in custody since her arrest on Dec 30 and attended the court in a green prison outfit, stood silently throughout the ruling, her head bowed.

She had pleaded not guilty to most of the charges, including physically assaulting the chief steward Park Chang Jin, who says she made him kneel and beg for forgiveness while jabbing him with a service manual.

Mr Park backed up the charges during his testimony in the formal trial hearing. He said Cho hustled a (female) flight attendant with some abusive words.

Cho was seen as emblematic of a generation of spoilt and arrogant offspring of owners of the giant family-run conglomerates, or chaebols, that dominate the South Korean economy.

Like Cho, many are given senior positions in the family business, sometimes after a token period "learning the trade".

In the past, chaebol owners have appeared to be above the law. Those convicted of gross fraud have either received lenient sentences or been granted pardons after just a short time in jail.

Cho resigned from all her posts and publicly apologised for her behaviour, which her father and KAL chairman Cho Yang Ho also criticised as a "foolish act".

The story hit international headlines and was seen as something of a national embarrassment, with South Korean media commentators suggesting Cho had shamed the country.

Multiple media outlets reported that Cho had submitted a number of letters to the court, expressing feeling of repentance and requesting leniency.

Meanwhile, the court also handed down jail terms to a Korean Air executive director and a Transport Ministry official, respectively.

The prosecution earlier indicted Korean Air executive director Yeo Woon Jin on charges of destroying evidence from the case. The 57-year-old was also accused of pressuring the cabin crew chief to minimise the case's impact.

A Transport Ministry official surnamed Kim was also charged for leaking information about the ministry's probe to the airliner.

Kim had reportedly phoned Yeo about 30 times and exchanged 10 text messages between Dec 7 and the day before the ministry's probe was launched, investigators said.

The civil servant, a close confidant of Yeo, was later found to have worked at Korean Air for 15 years as a flight attendant and chief purser.