The 7.62mm caliber round was detected during a security check before a flight from Incheon to Bangkok on Tuesday.
Airport police confiscated the bullet and allowed the female crew member to depart. They plan to question her upon her return.
Korean Air's internal inquiry suggests she did not intentionally attempt to bring the bullet onboard. The attendant reportedly brought an old pouch from her family home, unaware it contained the ammunition.
The airline pledged full cooperation with law enforcement and committed to enhancing safety awareness training for all employees.
The incident follows a similar occurrence in March when a 9mm bullet was found under a passenger seat on another Korean Air flight at the airport.
