Two people, both flight attendants, are the only survivors of the crash and are being treated at South Korean hospitals.

South Korean police raided the offices of Jeju Air and the operator of Muan International Airport Thursday, as the investigation into the deadly Dec. 29 plane crash that killed 179 people ramped up.

The flight was carrying 181 passengers and crew when it belly-landed before slamming into a barrier, killing all aboard except two flight attendants.

The Jeju Air crash in South Korea is an outlier in a country considered to be a gold standard for airline safety.

Ultimately, the plane crashed, killing 179 people in South Korea’s worst aviation disaster. A standard pre-flight inspection found “no issues” with the Jeju Air passenger plane before it crashed.

A South Korean Jeju Air passenger jet crashed on landing at Muan International Airport on Sunday, killing 179 people in the country's deadliest air disaster.

South Korean investigators probing a Jeju Air crash which killed 179 people in the worst aviation disaster on its soil said Wednesday they will send one of the retrieved black boxes to the United States for analysis.

South Korean police raided Jeju Air and the operator of the Muan airport as they ramped up their investigation into Sunday’s catastrophic plane crash that claimed 179 lives, marking the worst aviation disaster in the country’s recent history.

Investigators said they were close to finalising the transcript of the cockpit voice recorder from a fatal plane crash that left 179 people dead last week.

Jeju Air and the South Korean airline industry continue to feel the impacts of accidents beyond a reduced flight schedule. The airline currently has 260 billion won ($177 million) in deferred revenue from passengers who have booked their tickets but have not yet flown.

As first reported by Reuters, the US-based aerospace company will bring its technical expertise to the extensive multinational investigation of Jeju Air Flight 7C2216. Video footage of the ill-fated Jeju Air 737-800 appears to show smoke emanating from its right-hand engine, possibly due to a bird strike, although other factors are being looked at.