A flight from Cebu, Philippines, to Busan, South Korea, was forced to turn around after crews discovered mid-flight that the door to the Boeing 737 had been improperly closed, the South Korean Ministry of Land, Infrastructure, and Transport confirmed to ABC News.
Passengers on the Jin Air jet, carrying 163 people, later complained of numbness, headaches and ear pain at 10,000 feet.
"I thought I would die here, because I was numb with a headache," one passenger said in Korean.
In video shot by someone inside the cabin, the audio appears to capture what sounds like air swishing through the badly sealed door.
The airline said an initial investigation uncovered no defects in the jet.
"We will investigate in a thorough manner so that something like this will not happen again," said Cho Yang-ho, chairman of Korean Air, Jin Air’s parent company.
The South Korean transport ministry said it is also investigating the incident.
“All low-cost carriers will undergo an overall inspection of their safety management to prevent similar accidents,” the ministry said in a statement.