The cockpit voice recorder data on the Alaska Airlines Boeing 737 MAX 9 jet, which lost a panel mid-flight on Friday, was overwritten, U.S. authorities said, renewing attention on an industry call for longer in-flight recordings. National Transportation Safety Board (NTSB) chair Jennifer Homendy said on Sunday no data was available on the cockpit voice recorder because it was not retrieved within two hours – when recording restarts, erasing previous data. NTSB has called for that window to be increased to 25 hours, the European norm for planes made since 2021.
In the case of the 737 MAX that lost a door plug on its flight from Portland to Anchorage, NTSB investigators will use data from a separate recorder called a flight data recorder (FDR) to narrow down the area where they must look for the missing part. The NTSB also has asked Boeing to provide a detailed technical bulletin, which can take a few days.
Boeing has been working on the bulletin, which will include the details of the fuselage hole and what was found inside, a source familiar with the matter said. However, the company must submit it to the FAA for review and approval. Once that happens, the information can be distributed to employees worldwide.
NTSB officials have begun scouring the wreckage of the plane for the missing piece, which could give clues about what caused the violent decompression that blew the cabin door open and sucked items out of the aircraft, including headrests and seats. Homendy said the force of the incident ripped a headset from one pilot, and seat backs were torn off and scattered throughout the cabin.
Investigators believe that the missing part ripped off during the rapid decompression and came out of a small opening in the plane’s fuselage near the front. The NTSB has not determined what caused the opening to tear but says it is not a mechanical problem.
The exploding jet flew about 37,000 feet (11,000 meters), about as high as a passenger jet can go. The decompression would have dropped air pressure dramatically, and at that altitude, oxygen is usually scarce, if not nonexistent. Passengers and crew who were not wearing seatbelts could have been sucked out of the plane, and some may have died, experts say.
The NTSB is trying to determine whether the incident was a design or manufacturing problem. Pilots had reported pressurization warning lights on three flights of the specific Alaska Airlines 737 MAX 9 involved in the incident, and the airline restricted lengthy flights over water as a result. But the NTSB chairman said it was too early to know if that played a role in the incident. The incident led to the FAA grounding all 171 737 MAX 9s in the United States until they were inspected. Boeing is reviewing the issue but has yet to determine what went wrong.
