SEOUL - GE Aerospace, whose joint venture made the engines of the Boeing airplane that crashed in the deadliest aviation disaster on South Korean soil, joined the investigation as Seoul extended by a week special inspections of all 101 Boeing 737-800 jets.

The transport ministry extended to Jan10 its inspections following the crash of a Boeing 737-800 operated by Jeju Air that killed 179 people, Joo Jong-wan, the deputy transport minister for civil aviation, told a press briefing.

"Investigators are in the process of probing the cause of the accident by piecing together a puzzle," Joo added.

The inspections had initially been set to wrap up on Friday (Jan 3), but another ministry official said further checks would look into matters such as whether airlines spent sufficient time on maintenance and secured parts for repairs.

Video images on social media appear to show smoke emerging from the plane's right engine in the lead-up to the crash.

Sunday's flight from Bangkok to the southwestern county of Muan belly-landed and overshot the runway at the regional airport, exploding into flames after hitting an embankment.

The ministry has said it would examine engines, maintenance records and landing gear on all 737-800s, with serious violations leading to suspension of an airline's operations.

The plane's engines are produced by GE Aerospace's CFM International joint venture with Safran. A media representative for GE Aerospace did not immediately respond to Reuters' emailed question about the investigation.

The addition of a GE representative takes to 23 the size of the investigation team, including 12 Korean investigators and US representatives from Boeing and the US National Transportation Safety Board (NTSB).

While the cause of the disaster is still unclear, the crash could add to headaches faced by Boeing as the planemaker battles to restore the trust of customers following two fatal 737 MAX crashes, a mid-air panel blowout, and a seven-week strike.

Unanswered questions include 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.

South Korea's investigation team said two of its members would leave for the United States with the flight data recorder recovered on Monday to analyse the critical data with the NTSB.

Joo expected investigators to finish transcribing the cockpit voice recording from the doomed aircraft in the next several days, making a decision later on disclosure of the transcript.

The ministry also held an emergency meeting with the chief executives of 11 airlines, including top-ranked Korean Air Lines and Asiana Airlines, to discuss ways to beef up aviation safety.

South Korea's acting President Choi Sang-mok urged investigators on Friday to work swiftly to collect evidence from the crash scene and analyse data from the cockpit voice recorder.

On Thursday, police said they were searching Jeju Air and the operator of Muan International Airport. They banned the airline's chief executive, Kim E-bae, and an unidentified official from leaving the country.

Investigators also plan a special inspection of the location and materials of the airport landing system at airports elsewhere in South Korea by Jan 8.

Safety experts said the embankment, designed to prop up the navigation system that helps pilots make safe descents, was too rigid and too close to the end of the runway.

Investigators will analyse data on 107 mobile phones recovered from the crash site, including text messages, for clues to what happened before the crash, Yonhap News said.

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Source: Reuters