The High Court in Seoul ruled that the behaviour of Cho Hyun-Ah, the eldest daughter of the airline's chairman, had not resulted in a change of flight path -- the most serious charge against her -- and handed down a reduced suspended sentence.
Cho, who was a KAL vice president in charge of in-flight service at the time of the December 5 incident, had become enraged after a flight attendant served her some nuts in a bag, rather than on a plate.
In her original trial, the district court determined that an aircraft was "in flight" from the moment it began to move, and that in ordering the return to the gate Cho had violated aviation safety laws by illegally changing the plane's route.
But the High Court overturned that decision, ruling that the return to the gate "did not constitute a change" of flight path.
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Handing down a reduced sentence of 10 months, suspended for a period of two years, High Court judge Kim Sang-Hwan said the threat Cho's actions had presented to the safety and security of the aircraft was "modest".
But the court upheld her conviction for hampering the plane's operation and violence against the cabin crew.
Chief steward Park Chang-Jin had testified that Cho had made him kneel and beg for forgiveness while jabbing him with a service manual.
The flight attendant who served the now infamous nuts has since filed a civil lawsuit, alleging Cho attacked, threatened and screamed obscenities and then pressured her to cover up the incident by lying to government regulators.
Many South Koreans saw the 40-year-old Cho's behaviour as emblematic of a generation of spoilt and arrogant offspring of owners of the giant family-run conglomerates, or "chaebols", that dominate the national economy.