South Korean investigators focused on an airport embankment as they intensified investigations Tuesday into its deadliest domestic air accident.
Police meanwhile worked to identify victims and families of those killed in the Jeju Air crash demanded more information.
All 175 passengers and four of the six crew were killed when the Boeing 737-800 belly-landed and skidded off the end of the runway at Muan International Airport on Sunday, erupting in a fireball as it slammed into an embankment holding navigation equipment.
However, remarks in the airport's operating manual, uploaded early in 2024, said the embankment was too close to the end of the runway and recommended that the location of the equipment be reviewed during a planned expansion.
A Transport Ministry official said authorities would need to check the document before replying to questions.
On Monday, South Korea's Acting President Choi Sang-mok ordered an emergency safety inspection of the country's entire airline operation.
Impatience rose Tuesday among exhausted families gathered at the airport as they waited for the bodies of their loved ones to be released.
One bereaved relative, Park Han-shin, said the bodies being held in freezers were prepared for transfer to funeral homes but the process could take time and urged others to stay patient.
The National Police Agency said it was making all-out efforts to speed the identification of the five bodies still unknown, by allocating more personnel and equipment such as rapid DNA analyzers.
A "black box" flight data recorder recovered from the crash site was missing a key connector and authorities were reviewing how to extract its data, but retrieval of data from the cockpit voice recorder has begun, the Transport Ministry told briefings.
Inspections of all 101 B737-800s operated by South Korean airlines were set to wrap up by Jan. 3, though the airport would stay closed until Jan. 7, it added in a statement.
Representatives of the U.S. National Transportation Safety Board (NTSB), Federal Aviation Administration, and aircraft maker Boeing have joined the investigations.
In a statement, the NTSB said it sent three investigators to assist, some specialized in operational factors and airworthiness.
"If we need more specialists we will send them," Jennifer Homendy, its chair, said in an interview.
Crash investigators are considering possible factors such as bird strikes and disabled control systems on the aircraft to the pilots' apparent rush to attempt a landing soon after declaring an emergency, fire and transport officials have said.
Officials have also faced pointed questions about airport design features, particularly the large dirt-and-concrete embankment near the end of the runway used for navigation equipment.
The plane slammed into the embankment at high speed and erupted into a fireball. Bodies and body parts were thrown into surrounding fields and most of the aircraft disintegrated in flames.
"Unfortunately, that thing was the reason that everybody got killed, because they hit a concrete structure," Captain Ross "Rusty” Aimer, the chief executive of Aero Consulting Experts, told Reuters and they added, "It shouldn't have been there."
Transport Ministry officials said most South Korean airports were built based on International Civil Aviation Organization rules that recommend a 240-meter (262-yard) runway-end safety area.
However, a domestic law allows adjusting the location of some installations in a range that does not "significantly affect the performance of the facility."
"But we'll look into whether there are any conflicts in our regulations, and conduct an additional review of our airport safety standards," Kim Hong-rak, director general for airport and air navigation facilities policy, told a briefing.
The U.S. Federal Aviation Authority uses different standards, Kim added.
Muan International Airport's Airport Operations Manual said the navigation equipment, called "localizers", was installed too near the end of the runway, or just 199 meters from the crash site.
The document, prepared by Korea Airports Corp and uploaded on its website, said the airport authority should "review securing additional distance during phase two of Muan International Airport's expansion".
South Korean officials have previously said the structure was about 250 meters from the end of the runway itself, though a paved apron extends past that.
The runway design "absolutely (did) not" meet industry best practices, however, said John Cox, chief executive of Safety Operating Systems and a former 737 pilot, adding that they preclude any hard structure like a berm within at least 300 meters of the end of the runway.
Video showed the plane appearing to slow down and in control when it went off the runway, Cox said. "When it hits that berm is when it turns into tragedy."
