Seoul: Korean Air suspended the youngest daughter of its chairman, a sister of the infamous "nut rage" heiress, from her duties on Monday pending a police investigation of complaints she threw a cup of water at someone.
Cho Hyun-min, a senior vice president, faced pressure from the airline's unions to step down after media reports she threw water into the face of an advertising agency manager, sparking a public backlash.
"Korean Air has excluded senior vice president Cho Hyun-min from work and suspended her from duties as of April 16 until the outcome of the police investigation," the airline said in a statement.
Cho, also known as Emily Cho, apologised on Thursday for what she called her "foolish behaviour".
Korean Air said on Friday, in response to media reports Cho had thrown a water bottle at someone's face, she had thrown either a water bottle or a cup on the floor, but not at anyone's face.
On Monday, the airline said it was a cup.
Cho, speaking to TV channel MBC after she cut short a vacation overseas and arrived in back home on Sunday, denied she had thrown a cup of water at the manager's face but said she had "pushed" it.
She said her action was "foolish". It is the latest controversy to engulf the family that holds a big stake in South Korea's largest airline group.
Cho's elder sister Cho Hyun-ah, or Heather Cho, made headlines over a notorious "nut rage" incident in 2014, when she lost her temper over the way she was served nuts in first class before takeoff from New York.
Heather Cho demanded the flight crew chief be expelled from the plane after she was served macadamia nuts in a bag and not on a dish.
The South Korea-bound plane had to return to the gate.
Cho was sentenced to a year in jail for violating airline safety laws, but was released after five months.
She returned as an executive of Korean Air's hotel affiliate in March.
Her younger sister's tantrum has reignited public impatience with family-run conglomerates known as chaebol, over what some South Koreans see as unchecked bad behaviour by the rich and powerful, especially second and third-generation children of the founders.
"Founders of conglomerates are considered myths, sacred. They have legitimacy, because they built the conglomerates from nothing," said Chang Sea-jin, a business professor at Korea Advanced Institute of Science and Technology.
"But second-generation and third-generation leaders do not have such legitimacy. They are simply born with 'golden spoons' in their mouths," he said.
Korean Air's employee union and two pilots' unions said on Sunday Cho Hyun-min's action harmed the airline's reputation and they wanted her to step down and offer a sincere apology to all of the company's approximately 20,000 employees and the public.
"Why must our employees feel shame? Why must our employees, who have committed no crime, be the subject of criticism?" the unions said. Cho apologised to employees in an email on Sunday, according to a copy seen by Reuters.
"As I was focusing on my passion for the work, I was unable to control my thoughtless words and deeds, through which I caused injury and disappointment for a lot of people," she said.
Korean Air confirmed that the email was sent to all employees, but declined to comment further.
Traditionally loyal to their employers and reluctant to become whistleblowers, more employees are now reporting problems, encouraged by growing public and government calls to reform chaebols in the wake of corruption scandals, said Park Ju-gun, the head of corporate analysis firm CEO Score.
Former president Park Geun-hye was sentenced to 24 years in jail this month on charges of receiving or demanding bribes from top conglomerates including Samsung and Lotte.
"The environment has changed. The government has changed," Park Ju-gun said.
Dozens of petitions demanding that Cho be punished and the word "Korean" removed from the airline's name have been posted on the presidential Blue House's online petition page.
One petition calling for the change to the company's name had 50,182 signatures by mid-day.
Shares in Korean Air Lines ended down 2.5 per cent while shares of its home rival Asiana Airlines rose 4.1 per cent.