Cho Hyun-Ah was jailed for a year in February after a district court found her guilty of violating aviation safety by forcing a taxiing New York-Seoul Korean Air Lines (KAL) flight to return to its departure gate.
Crucially, the lower court ruled that an aircraft should be deemed "in flight" from the moment it begins to move.
So even though the KAL aircraft had barely left the gate when she forced it to return, Cho was found guilty of illegally altering the plane's flight.
"It's hard to say that her act actually hindered security and the plane's safety," Yoo said. "She really had no intention to impede the plane's safe flight."
At the end of the hearing, Cho, who was dressed in a light-green prison outfit, stood and spoke to the packed courtroom, voicing remorse over her behaviour.
"On this occasion, I apologise again to the victims and beg for their forgiveness," she said.
She lambasted the chief steward over the behaviour of his cabin crew and then insisted the plane return to the gate so he could be removed from the flight.
The 40-year-old's actions invited overseas ridicule and domestic embarrassment.
Many South Koreans saw her 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.
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.
At the February trial Cho was acquitted of obstruction of justice charges, but the prosecution has appealed that decision and asked for her one-year prison term to be extended.
