Boeing 737-800 is among the most common aircraft in the world

Accident investigators are trying to find out what caused the Jeju Air flight to land without its landing gear down at Muan International Airport in southwestern South Korea, killing all but two of the 181 people on board as it burst into flames in the world's worst air disaster in the country in decades.

The acting president of South Korea, Choi Sang-mok, ordered a state of emergency study the country Boeing 737-800s, the type of plane used on the fatal Jeju Air flight 7C2216.

The Boeing 737-800 is one of the most common aircraft in the world, and has a strong safety record. It is before the Boeing 737 Max, the type involved two fatal accidents in 2018 and 2019 that killed all 346 people on board these flights. The highest was 737 established for almost two yearsand there was a flight control system, which was later modified linked to these two accidents.

Nearly 4,400 of the older Boeing 737-800s are in operation worldwide, according to aviation data company Cirium. That means the model makes up about 17% of the world's in-service commercial passenger jet fleet.

The average age of the world's 737-800 fleet is 13 years old, according to Cirium, and the last of the series of aircraft was delivered about five years ago.

Jeju Air took delivery of the plane involved in the crash this weekend in 2017. It was previously operated by European discount carrier Ryanair, according to Flightradar24. The plane involved in the accident was about 15 years old.

Aviation experts say investigators are unlikely to find a design problem with the long-flown plane.

“The idea that they would find a design flaw at this point is unbelievable,” said Richard Aboulafia, managing director at AeroDynamic Advisory, an aviation consulting firm.

A full investigation could take more than a year, and the unusual incident has raised more questions than answers, such as why the landing gear was not deployed. Even with dehydration, Boeing 737-800 pilots can manually lower the landing gear.

One theory involves a bird strike that could have disabled at least one if not both engines.

“If that happened at the height they were at, they probably didn't have time to do emergency checklists,” said Jeff Guzzetti, a retired aviation safety inspector with the US National Transportation Safety Board. and the Federal Aviation Administration. He also said that if the plane had not crashed into dirt and a hard wall at the end of the runway, the accident could have been longer. In that area there was a localizer that helps guide planes.

The NTSB is leading a team of US investigators that also includes Boeing and the FAA, because the aircraft was manufactured and tested in the United States.

Under international protocols, the country where the accident occurred will be in charge of the overall investigation.

Boeing shares fell more than 4% early Monday after local officials call for inspections on 737-800s operated by South Korean airlines, but pared losses earlier in the day down 2.3%.