More than half of the same model of the plane doesn't have an auxiliary power supply.

It is estimated that the black box of the Muan Airport plane was not recorded in the last four minutes due to the power supply cutoff, and more than half of the same models operated in Korea do not have auxiliary batteries for voice recorders.

According to the data submitted by the Ministry of Land, Infrastructure and Transport to Ahn Tae-joon's office of the National Assembly's Land, Infrastructure and Transport Committee, 56 of the 101 B737-800 models operated by six domestic airlines were found to have no auxiliary power supply in the control room voice recorder (CVR) in case of an emergency.

The black box auxiliary power supply is a device that can provide about 10 minutes of power to the black box when the aircraft's power is stopped, and due to the International Civil Aviation Organization (ICAO) and the Ministry of Land, Infrastructure and Transport's notice, it has been mandatory to install aircraft introduced in Korea since January 2018.

An official from the Ministry of Land, Infrastructure and Transport said it will check whether all aircraft introduced in Korea before 2017 will be installed with auxiliary power supplies, and it will also consider whether additional installations can be made.