A terrible plane crash in South Korea Sunday morning has resulted in the deaths of 179 people of 181 on board in one of the worst aviation disasters in the country’s history. While theories have been put forward, the exact cause of the crash is not yet known. It may take months for the full picture to emerge.

Jeju Air Flight 2216 crashed at Muan International Airport shortly after 9:00 a.m. on Sunday. The airport is located in Muan County, South Jeolla Province in the southwestern part of the country. It is the worst aviation accident for South Korea since 1997 when a Korean Air flight crashed in Guam killing 229 people out of 254 onboard.

The flight, which departed from Bangkok, Thailand, was carrying 175 passengers and six crew members. All but two of the passengers were South Korean nationals, the others being from Thailand. The two survivors were crew members who were in the tail section. They have been hospitalized in Seoul, but are reportedly recovering.

Jeju Air is one of a number of low-budget airlines based in South Korea that operate throughout East Asia. The company acquired the plane that crashed, a Boeing 737-800, in 2017 after it was operated by Ryanair from 2009 to 2016. The 737-800 is considered a relatively safe aircraft in comparison to the 737 Max, which has been connected to numerous accidents.

At present, the crash is being attributed to a bird strike that disabled one of the plane’s engines, resulting in a loss of power to hydraulic systems responsible for lowering the landing gear. Shortly before the crash, the airport’s control tower issued a bird strike warning. The pilot of the aircraft sent a distress call approximately two minutes later at 8:59 a.m.

The pilot made an initial attempt to land, but was unable to do so. The crash occurred at 9:03 on the second landing attempt, without any of its landing gear deployed or brake flaps in the proper position to slow the plane’s high speed. It skidded across the runway before smashing into an embankment, and bursting into flames.

Fire and rescue crews, which typically would be ready for such an emergency landing, were not prepared. The placement of the embankment has been called into question, with some aviation experts suggesting it was uncommon and unnecessary.

According to the Hankook Ilbo, a least one passenger sent text messages to a family member waiting at the airport, saying, “A bird struck the wing and we can’t land.” Yu Jae-yong, an eyewitness staying at a pension near the airport, told Yonhap News Agency, “I saw the plane fly over the pension and there were sparks coming from the right wing engine. I was telling my family there was a problem and then I heard an explosion.”

A firefighting official told the media: “After the plane collided with the wall, passengers were thrown out of the aircraft. The chances of survival are extremely low. The aircraft has almost completely been destroyed, and it is difficult to identify the deceased. We are in the process of recovering the remains, which will take time.”

Acting President Choi Sang-mok declared Muan a special disaster zone, which makes the county eligible for state support. He said on Sunday, “We will thoroughly investigate the cause of the accident and devise preventive measures to avoid the occurrence of similar accidents in the future.” He ordered an investigation into South Korea’s airline safety systems.

While a bird strike likely occurred, aviation experts have suggested that other factors may have contributed to the accident. Damage to a single engine should not have knocked out the plane’s whole system. The second engine should have been sufficient to power the landing gear systems.

Marco Chan, a former pilot and senior lecturer in aviation operations at Buckinghamshire New University, told Reuters, “Of course there might have been a bird strike. But the consequences are much too big for that to be the direct cause of the accident.”

Kim In-gyu, director of the Korea Aerospace University Flight Education Center, explained to the Yonhap News Agency, “We need to analyze the cause, but it’s very unusual for all three landing gears to fail to deploy. It is difficult to conclude that a bird strike alone was responsible. We also need to examine whether the aircraft had any pre-existing defects.”

Jeju Air CEO Kim I-bae was quick to claim that no problems were discovered during the plane’s routine maintenance check and that no abnormal conditions were reported when the plane took off from Bangkok.

However, the day before the accident, the aircraft operated flights shuttling back and forth between Muan and Kota Kinabalu, Malaysia; Nagasaki, Japan; Taipei, Taiwan; and Bangkok, Thailand, totaling eight take-offs with little downtime. This has raised questions about Jeju Air’s maintenance procedures.

In order to maximize flights and boost profits, Jeju Air pushes its crews to use only the “minimum maintenance time” of 28 minutes between flights required for the 737—the time set by South Korea’s Ministry of Land, Infrastructure and Transport. Lack of time means that faults can be missed. In 2021, a Jeju Air plane took off after damage sustained during its previous landing went unnoticed.

A mechanic, who has worked on aircraft like 737s for low-cost airlines, explained to the Hankook Ilbo that the 28-minute time limit means workers essentially perform a walk-through, not a detailed inspection. “After all the passengers… disembarked, 28 minutes is the time it takes a mechanic to go into the cockpit and confirm there are no warning lights and look with a naked eye that there is no damage to the interior and exterior fuselage.”

On Monday morning, a day after the crash, another of Jeju Air’s 737-800s experienced a landing gear issue. The flight took off from Gimpo International Airport in Seoul and returned safely shortly afterwards. But the fault suggests that the airline has taken little action to ensure another tragedy does not occur.