South Korean police have raided Jeju Air and the operator of Muan International Airport as part of their investigation into Sunday's crash that killed 179 people in the worst aviation disaster on the country's soil.
Jeju Air 7C2216, which departed the Thai capital of Bangkok for Muan in southwestern South Korea, belly-landed and overshot the regional airport's runway, exploding into flames after hitting an embankment.
Two crew members, who were sitting in the tail end of the Boeing 737-800, were pulled out alive by rescuers but injured.
Jeju Air was co-operating with police, the airline said, as police raided its office in Seoul. (AP PHOTO)
The conversion of data from the cockpit voice recorder to audio files, which could provide critical information on the final minutes of the flight, was completed on Thursday, Joo Jong-wan, the deputy transport minister for civil aviation, told a media briefing on Thursday.
Police investigators were searching the offices of the airport operator and the transportation ministry aviation authority in the southwestern county of Muan, as the well as office of Jeju Air in Seoul, the South Jeolla provincial police said in a media statement.
Investigators planned to seize documents and materials related to the operation and maintenance of the aircraft as well as the operation of airport facilities, a police official told Reuters.
Jeju Air was co-operating with the police, a director at the airline, Song Kyeong-hoon, told a media briefing.
Questions by air safety experts on what led to the deadly explosion have focused on the embankment, designed to prop up the "localiser" antenna used to guide landings, which they said is too rigid and too close to the end of the runway.
"This rigid structure proved catastrophic when the skidding aircraft made impact," said Najmedin Meshkati, an engineering professor at the University of Southern California, adding it was concerning that the navigation antenna was mounted on "such a formidable concrete structure, rather than the standard metal tower/pylon installation".
Joo said the ministry was still unable to provide clear details on Muan airport's upgrade plans that had led to the addition of the structure to support the navigation system.
Questions by air safety experts have focused on the embankment at the end of the runway. (AP PHOTO)
The ministry was checking localiser equipment at airports throughout the country, Joo said.
A probe into the doomed Jeju Air flight is also under way involving South Korean officials and the US National Transportation Safety Board (NTSB), Federal Aviation Administration (FAA) and the aircraft's maker, Boeing.
It remains unanswered why the aircraft did not deploy its landing gear and what led the pilot to apparently rush into a second attempt at landing after telling air traffic control the plane had suffered a bird strike and declaring an emergency.
The aircraft's flight data recorder, which was damaged, is being taken to the United States for analysis in co-operation with the NTSB.
Investigators from the NTSB, FAA and Boeing are in South Korea to help the probe.
South Korean Acting President Choi Sang-mok said in a disaster management meeting immediate action must be taken if a special inspection of all Boeing 737-800 aircraft operated in the country finds any issues.
"As there's great public concern about the same aircraft model involved in the accident, the transport ministry and relevant organisations must conduct a thorough inspection of operation maintenance, education, and training," Choi said.