WASHINGTON (Reuters) -The U.S. National Transportation Safety Board will hold a hearing on Tuesday to determine the probable cause of a mid-air cabin panel blowout of a new Boeing 737 MAX 9 flight in January 2024 that spun the planemaker into a major crisis.

The board is expected to harshly criticize Boeing's safety culture and its failure to install four key bolts in a new Alaska Airlines MAX 9, officials told Reuters.

NTSB Chair Jennifer Homendy has said the incident was entirely avoidable because the planemaker should have addressed unauthorized production work long ago.

"This accident should have never happened. This should have been caught years before," Homendy said last August during a two-day investigative hearing. "The safety culture needs a lot of work."

The accident prompted the Justice Department to open a criminal investigation and declare that Boeing was not in compliance with a 2021 deferred prosecution agreement and CEO Dave Calhoun announced he would step down within a few months of the mid-air panel blowout.

The incident badly damaged Boeing's reputation and led to a grounding of the MAX 9 for two weeks and a 38 planes per month cap by the Federal Aviation Administration on MAX production that still remains in place.

Boeing created no paperwork for the removal of the 737 MAX 9 door plug - a piece of metal shaped like a door covering an unused emergency exit - or its re-installation during production, and did not know which employees were involved, the NTSB said last year.

Boeing did not respond to a request for comment ahead of the meeting.

Then-FAA Administrator Michael Whitaker said in June 2024 the agency was "too hands off" in Boeing oversight and it has boosted the number of inspectors at Boeing and Spirit AeroSystems factories.

Boeing had agreed last July to plead guilty to a criminal fraud conspiracy charge after two fatal 737 MAX crashes in Indonesia and Ethiopia. But it last month struck a deal with the Justice Department to avoid a guilty plea.

The Justice Department has asked a judge to approve the deal, which will allow Boeing to avoid pleading guilty or facing oversight by an outside monitor but will require it to pay an additional $444.5 million into a crash victims fund to be divided equally per crash victim.