Smoke rises from the tail section of a Jeju Air Boeing 737-800 series aircraft after the plane crashed and burst into flames at Muan International Airport in South Jeolla Province, some 288 kilometers southwest of Seoul on December 29, 2024. YONHAP via AFP

SEOUL — The official cause of the crash of a Jeju Air plane in South Korea last week that killed 179 of the 181 aboard is still not known.

Authorities including American officials are scrambling to establish why the Boeing 737-800 belly-landed before slamming into a concrete barrier in a fireball at Muan International Airport.

Here is what we know about the final minutes before the worst-ever air disaster on the country's soil.

Bird strike

At 8.54 am (2354 GMT) on Sunday, Jeju Air flight 2216 heading from Bangkok's Suvarnabhumi Airport received permission to land in Muan.

Three minutes later, air traffic control warned the pilot about "bird activity" in the area.

Two minutes later, at 8.59 am, the pilot made a desperate mayday call, declaring "bird strike, bird strike", the transport ministry said.

According to an opposition lawmaker citing data from the Korea Airports Corp, Muan has the highest bird strike rate nationwide, with 0.09 percent of its 11,004 flights during that period experiencing incidents.

Still, experts have noted the rarity of bird strikes leading to malfunctions of key systems of an airplane.

"It isn't common that a bird strike leads to both engines of the plane failing, but it looks like it may have been the case here," said Goo Nam-seo, aerospace professor at Seoul's Konkuk University.

"A plane can function normally with just one engine, but both could have failed here."

Officials said they would investigate whether the airport complied with regulations about preventing bird strikes.

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Abandoned landing

On the hour, the pilot abandoned a landing attempt.

Air traffic control then proposed the pilot land in the opposite direction, which the pilot accepted.

At 9:02 a.m., the plane approached for a second landing attempt, seemingly without undercarriage.

It struck the ground around 900 to 1,200 meters (2,952 to 4,000 feet) along the 2,800-meter runway.

Landing gear

The landing gear would have typically been put down, but it malfunctioned, meaning the pilot had to belly land.

It overran the runway and hurtled towards the end of the embankment.
South Korean fire officials and the transport ministry said the possible bird strike may have disabled the plane's landing gear.

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Concrete wall

At 9:03 a.m., the plane overran the runway and skidded into a large embankment made of dirt and concrete and housing an instrument guidance system known as a localizer.

Video footage showed the plane smashing into the installation, which was located 250 meters past the end of the tarmac.

Questions have been asked over why the localizer was installed at the end of the runway, which experts say poses a danger in case of a plane overrun.

The transport ministry has launched a separate inquiry into how the structure may have contributed to the scale of the accident.

Local media reports said its installation may have violated local rules mandating that all structures installed on airport grounds must be made up of easily breakable material.

Final conversations

Investigators have also recovered two black boxes from the plane.

Joo Jong-wan, the country's deputy minister for civil aviation, said investigators were able to extract audio data from the plane's cockpit voice recorder to hear the pilots' final conversations.

The flight data recorder, however, sustained damage to a connector linking it to the power supply and will be sent to the United States for analysis.

What next?

The government has ordered an emergency inspection of all Boeing 737-800 models flown by Korean airlines, and also of runways at national airports.

The transport ministry said it may take between six months to three years to determine the precise cause of the crash.

The investigation is headed by South Korean air safety officials, with assistance of the US Federal Aviation Administration, which frequently aids with probes into global plane crashes. 

© Agence France-Presse 

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