South Korean authorities on Tuesday said they were investigating the role of a concrete barrier at the end of Muan airport runway in the country's worst air disaster, which killed 179 people as a Jeju Air jet crashed on landing.

US investigators, including from Boeing, were 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.

The plane was carrying 181 people from Thailand to South Korea when it made a mayday call and belly-landed before hitting the barrier and bursting into flames, killing everyone aboard except two flight attendants pulled from the burning wreckage.

Acting South Korean President Choi Sang-mok, who has only been in office since Friday, said the accident 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."

Officials initially pointed to a bird strike as a possible cause, but experts have also flagged the barrier, with dramatic video showing the Boeing 737-800 bursting into flames as it collides with it.

When asked whether it was permissible for the airport to have used concrete in the barrier, director-general for airport policy Kim Hong-rak said the government would "review the relevant regulations and their application".

"Whether this structure exacerbated the damage is... something the Accident Investigation Committee plans to investigate thoroughly," said deputy minister for civil aviation, Joo Jong-wan.

"At this stage, it is important to avoid focusing solely on any particular factor as the definitive cause of the accident," he said, adding investigators were reviewing "all potential scenarios to ensure a thorough investigation."

Jeju Air CEO Kim E-bae said that there were "no specific or unusual issues during the maintenance process" of the aircraft.

"As for whether the landing gear functioned properly, that is directly related to the accident investigation, and we are not in a position to know at this time," he told a press conference.

South Korea is observing seven days of mourning over the disaster, with New Year celebrations cancelled and flags flying at half-mast. (AFP)