Bolts that helped secure a panel to the frame of a Boeing 737 Max 9 were missing before the panel blew off the Alaska Airlines plane last month, according to accident investigators.

The National Transportation Safety Board issued a preliminary report on the Jan. 5 incident Tuesday.

The report included a photo from Boeing, which worked on the panel, which is called a door plug. In the photo, three of the four bolts that prevent the panel from moving upward are missing. The location of the fourth bolt is obscured.

The investigators said that the lack of certain damage around the panel indicates that all four bolts were missing before the plane took off from Portland, Oregon.

Pilots were forced to make a harrowing emergency landing with a hole in the side of the plane.

Without the bolts, nothing prevented the panel from sliding upward and detaching from “stop pads” that secured it to the airframe.

Honda is recalling more than three quarters of a million vehicles in the U.S. because a faulty sensor may cause the front passenger air bags to inflate when they’re not supposed to.

The recall covers certain Honda Pilot, Accord, Civic sedan, HR-V and Odyssey models from the 2020 through 2022 model years, as well as the 2020 Fit and Civic Coupe. Also included are the 2021 and 2022 Civic hatchback, the 2021 Civic Type R and Insight, and the 2020 and 2021 CR-V, CR-V Hybrid, Passport, Ridgeline and Accord Hybrid.

Affected models from the Acura luxury brand include the 2020 and 2022 MDX, the 2020 through 2022 RDX and the 2020 and 2021 TLX.

Dealers will replace the seat sensors at no cost to owners. Owners will be notified starting March 18.