The flight recorder of the Jeju Air passenger jet that crashed last month, killing 179 people, stopped recording for its last four minutes, South Korean officials said on Saturday, a significant setback for investigators.
Data extracted from the so-called black box, consisting of the cockpit voice recorder and the flight data recorder, is generally crucial in investigations of aviation accidents. Officials in South Korea, who have been working with the United States’ National Transportation Safety Board, have said that the flight data for the plane’s last four minutes would be especially important in this crash.
But on Saturday, South Korea’s Ministry of Land, Infrastructure and Transport said that for reasons not yet determined, the black box of the Boeing 737-800 had stopped recording then.
“We plan to investigate why the data was not recorded,” the ministry said in a news release. It also said that other data and analysis would be used to try to understand what happened in last month’s disaster.
Jeju Air Flight 7C2216, coming from Bangkok with 181 people on board, was preparing to land at Muan International Airport in southwestern South Korea at 8:59 a.m. on Dec. 29 when its pilot reported, “Mayday, mayday, mayday,” and, “Bird strike, bird strike,” according to officials. The pilot also told the air traffic control tower that he was “going around,” meaning he would abort his first landing attempt and circle in the air to prepare for a second one.
But he apparently did not have enough time to make a full circle. Instead, the plane approached the runway from the opposite direction and landed on its belly, without its landing gear deployed. Seeming unable to control its speed, it overshot the runway. Four minutes after the Mayday emergency report, the plane slammed into a concrete structure off the southern end of the runway and exploded into flames.
A key question has been: What happened during those four minutes?
“The black box data is crucial in the investigation,” said Hwang Ho-won, the chairman of the Korea Association for Aviation Security. “If the investigators don’t have it, it will create a serious problem for them.”
The missing data adds mystery to the crash, which was the worst aviation disaster on South Korean soil and the deadliest worldwide since that of Lion Air Flight 610 in 2018, when all 189 people on board died.
Mr. Hwang said black boxes could be damaged by impact, fire or prolonged exposure to deep water. But it was hard to explain how the Jeju Air black box failed to record in its last four minutes, he said.
He said that investigators might be able to reconstruct part of the conversation inside the cockpit based on interviews with control tower officials. Radar and other data suggested that the plane tried but failed to gain altitude after reporting a bird strike and hurried to land, Mr. Hwang said.
Investigators have said they were looking into various possibilities, including that of the plane losing use of one or both of its engines in its last minutes.
Most of the 179 people who died were South Koreans returning home from a Christmas holiday in Thailand. The two survivors were both crew members found with injuries in the plane’s tail section.
The disaster prompted a national outpouring of grief, with memorials set up across South Korea, and came as the country was also dealing with a political crisis set off by President Yoon Suk Yeol’s short-lived imposition of martial law and his impeachment by Parliament.