South Korea said it was examining regulations around a concrete wall at Muan airport, after a Jeju Air flight crashed into the barrier and burst into flames, killing 179 people.
When asked whether it was permissable for the airport to have used concrete - which experts have flagged as unsafe - director-general for airport policy Kim Hong-rak said the government would "review the relevant regulations and their application".
Meanwhile, authorities have begun releasing the bodies of victims to families, as investigators try to determine why the Jeju Air Boeing 737-800 crash landed.
US investigators, including from Boeing, arrived at the crash site in southwestern Muan, officials said, as South Korean authorities began assessing two black boxes retrieved from the burned out wreckage of the aircraft.
Jeju Air Flight 2216 was carrying 181 people from Thailand to South Korea when it made a mayday call and belly-landed before crashing into a barrier and bursting into flames.
Just two people, both crew members, survived.
South Korea is observing seven days of mourning, with flags flying at half mast.
Acting President Choi Sang-mok, who has only been in office since Friday, said the incident was a "turning point" for the country, calling for a full overhaul of air safety systems.
He urged officials to "thoroughly re-examine the overall aircraft operation system ... and immediately address any necessary improvements".
"Today marks the final day of 2024," he said, urging citizens to "reflect on the past year and prepare for the new one".
"I am well aware that whenever challenges arose, both domestically and internationally, all citizens and public officials united with one heart and mind to overcome these crises," he added.
At Muan airport, investigators combed over the wrecked fuselage and soldiers picked carefully through the fields around the airport, as people left ritual offerings for victims - including food and letters - near the airport's perimeter.
"Captain, first officer and crew members, thank you so much for doing your best to save the passengers. I pray for your eternal rest," one letter left on the fence said.
Inside the airport, where victims' relatives have been camped out since Sunday, waiting for information, anger was growing over delays in identifying passengers on the plane.
But officials said they had begun releasing the first bodies to relatives, even as work to identify all victims continued.
"Of the 179 victims, the bodies of four have completed the handover procedures to their bereaved families for funerals," transport minister Park Sang-woo said at Muan International Airport.
"For 28 victims, whose identities have been confirmed and autopsies completed, we will allow funeral procedures to begin from 2pm (5am Irish time) today with the consent of their families," he added.
One family lost nine members - including the oldest passenger on the plane, who was taking his first ever overseas trip to celebrate his birthday, local broadcaster KBC reported.
The passenger, surnamed Bae, was travelling with his wife, his two daughters, one son in law and four grandchildren, including a five-year-old.
The entire family was killed, except one of the daughter's husbands - who was not able to join the trip, and now faces the loss of his wife and three children.
"Yesterday, the village chief went to Muan Airport and said the son-in-law was in utter despair, saying, 'I should have gone with them and died with them'," KBC said.
Memorial altars for the victims have been set up nationwide, including in Seoul.
At Muan airport, families were overseeing the set up of a new altar, with black and white funeral flowers filling the area.
A fuller account of what went wrong in the flight's final moments is expected once authorities have analysed the black boxes.
"Regarding the black box, surface contamination cleaning has been completed at the testing and analysis center and its condition is currently being assessed," deputy civil aviation minister Joo Jong-wan said.
"However, the flight data recorder's data storage unit is still under evaluation," he said, as it was found with a missing connector.
Technical reviews are under way to determine how to extract the data.
