Boeing said on Tuesday it plans to make design changes to prevent a future mid-air cabin panel blowout like the one in an Alaska Airlines 737 MAX 9 flight in January that spun the planemaker into its second major crisis in recent years.

The head of the US National Transportation Safety Board grilled Boeing Co. executives on why the planemaker didn’t address quality lapses in its factories well before a midair blowout on one of its jets early this year.

Top Boeing executives are set to testify during two days of hearings examining breakdowns that led to the mid-air blowout aboard a 737 Max jet in January.