The airport had been due to reopen on Tuesday following the Dec 29 crash.

A joint investigation team is stepping up the probe into South Korea’s deadliest air crash. Two of the Korean investigators on Monday are set to leave for the US with flight data recorders for analysis with the US national transportation safety board.

The flight data recorder, along with the cockpit voice recorder, are the two black boxes that contain key information about the crash.

Investigators compiled the complete transcript from the cockpit voice recorder recovered from the wreckage of the Jeju Air Boeing 737-800 on Saturday. It is not clear whether they will disclose the transcript.

Investigators retrieved two of the plane’s engines over the weekend, as a representative from engine maker GE joined the probe. The transport ministry extended its inspections of all the Boeing 737-800 planes operated by Jeju Air and five other airlines in the country to Jan 10, including their maintenance records.