South Korea’s authorities investigating last month’s Jeju Air plane crash have submitted a preliminary accident report to the UN aviation agency and to the authorities of the United States, France and Thailand.

The investigation into the deadliest air disaster on the country’s soil remains ongoing, the report made available on Monday, January 27, 2025, said, focused on the role of “bird strike” and involving an analysis of the engines and the “localizer” landing guidance structure. “These all-out investigation activities aim to determine the accurate cause of the accident,” it said.

The International Civil Aviation Organization (ICAO), the UN agency, requires accident investigators to produce a preliminary report within 30 days of the accident and encourages a final report to be made public within 12 months.

The Boeing 737-800 jet, from Bangkok and scheduled to arrive at Muan International Airport, overshot the runway as it made an emergency belly landing and crashed into the localizer structure, killing all but two of the 181 people and crew members on board on December 29, 2024.

The localizer, which aids navigation of an aircraft making an approach to the runway, and the structure built of reinforced concrete and earth at Muan airport supporting the system’s antennae was likely a cause of the disaster, experts have said.

The report confirmed that bird strikes played a role in last month’s fatal crash of a Jeju Air plane, although the precise cause remained under investigation.

The report highlighted much of the initial findings by the South Korean investigators that was shared with the families of the victims on Saturday, including the pilots discussing a flock of birds they spotted on its final approach.

The exact time of a bird strike reported by the pilots remains unconfirmed, the accident report said, but the aircraft “made an emergency declaration for a bird strike during a go-around.”

Feathers, Blood Stains Found In Both Engines

The preliminary investigation report revealed that feathers and blood stains from birds were found in both engines of the Boeing 737-800 which crashed on 29 December, killing 179 of the 181 passengers and crew members onboard. “Both engines were examined, and feathers and bird blood stains were found on each,” it said.

According to the report, a DNA analysis identified the bird remains as those of Baikal Teals, a migratory duck species.

It didn’t offer any conclusions about what might have caused the plane to land without its landing gear deployed or why the flight data recorders stopped working in the final four minutes. “After the crash into the embankment, fire and a partial explosion occurred. Both engines were buried in the embankment’s soil mound, and the fore fuselage scattered up to 30-200 meters from the embankment,” it said.

Investigators said that air traffic controllers had warned the pilot about potential bird strikes barely two minutes before the aircraft sent a distress signal, which confirmed that a bird had struck the plane.

Shortly after, the pilot attempted an emergency landing.

The report does not say what may have led to the two data recorders to stop recording simultaneously just before the pilots declared mayday.

The aircraft was at an altitude of 498 ft (152 metres) flying at 161 knots (298 km/h or 185 mph) at the moment the blackboxes stopped recording, it said.

Investigators yet to determine why.

Further analysis was underway to assess the plane’s failure to deploy its landing gear, which caused it to skid off the runway and ram into a concrete structure.

Aviation experts said the structure should have been made with lighter materials that could break more easily upon impact.

In the wake of the accident, South Korean authorities announced they would replace the structure with a one that would break more easily upon impact.

It was also reported that the country would change similar structures at eight other airports.