The former vice president of Korean Air Lines Co. will appear before aviation safety inspectors on Friday to answer questions about forcing a flight crew member to deplane over snack-serving etiquette, the company said Thursday, as an investigation widens over the "nut case" amid public outrage.

Cho Hyun-ah has become the focal point of the public anger as the eldest daughter of Korean Air Chairman Cho Yang-ho took issue with an attendant's serving nuts in bags and ordered a senior crew member to deplane from a Korean Air flight from New York to Seoul last Friday.  

Her action, which forced the aircraft to stop taxiing and return to its gate at John F. Kennedy International Airport, prompted the transportation ministry to look into the case. The 40-year-old apologized and stepped down from her post as vice president of flight services.

"Cho will actively cooperate with the investigation to help the transportation ministry get to the bottom of the case," Korean Air, South Korea's largest air carrier, said.

Cho will appear at the aviation safety inspectors' office at the Gimpo International Airport in western Seoul at 3 p.m. on Friday, the company said.

Cho initially refused to show up, citing her fragile emotional state, but gave in to pressure after prosecutors on Thursday raided Korean Air's headquarters in Seoul and its branch office at Incheon International Airport. 

The prosecution separately started its probe after a local civic group filed a petition against Cho, accusing her of breaking the law by causing a disturbance. Violating aviation security rules can result in fines or, in serious cases, the perpetrator can face criminal charges.

"We will question whether (Cho) shouted at and used abusive language with the flight attendant, and why she returned the flight to the gate and deplaned a crew member," said Lee Kwan-hee, an aviation safety official at the Ministry of Land, Infrastructure and Transport.

Aviation authorities have been questioning the captain, the purser and flight attendants, and plan to question passengers who were sitting near Cho to get details of the incident.

Cho screamed at the flight attendant for not asking her if she would like a preflight snack of macadamia nuts, and then for committing the egregious act of serving them in a paper bag rather than on a plate, according to reports. Korean Air earlier confirmed that Cho raised her voice when chastising the crew member.

The ministry is also trying to obtain records of the Korean Air jet's movements at JFK Airport, including radio communication between the Korean Air pilot and the airport control tower.

The flight, already taxiing, returned to the gate to allow the purser to disembark, causing a delay in the departure time of the plane carrying 250 passengers bound for Incheon International Airport. Officials said the return to the gate delayed departure by 16 minutes, with the plane arriving 11 minutes behind schedule at Incheon International Airport.

The ministry said that if Cho did cause a commotion and threatened the crew, such actions could be in violation of the country's aviation law and rules governing aircraft security, noting: "If the law was broken, firm action will be taken against the offender." (Yonhap)