From Investing.com:

Alaska Airlines is cooperating with a DOJ investigation into a Boeing 737 MAX blowout on a January flight. The investigation is to determine if Boeing complied with a previous settlement following two fatal crashes. The incident prompted the temporary grounding of 171 MAX 9 jets. Alaska Airlines resumed MAX 9 service after completing inspections. The missing door panel bolts were manufactured by Spirit AeroSystems.



Read more at Investing.com: Alaska Airlines cooperates with DOJ in Boeing 737 MAX blowout probe By Reuters