According to information from the NTSB (National Transportation Safety Board) inspections turned up other 737-9 (Max) aircraft with loose door plug bots. The inspections were done by United and Alaska air, following last Friday's door plug blowout on a plane headed from Portland to CA.

  NTSB says loose bolts found

According to the AP and, it is possible the four bolts that hold what is called a door plug in place might have been missing on Flight 1282 that had to make an emergency landing in Portland Friday evening.

The NTSB says United and Alaska both reported finding several other 737 planes with loose bolts. On aircraft that have less than 200 passengers, the airlines use what is called a door plug, because they don't require as many exits.

These door plugs are designed so they can be removed if needed, according to MyNorthwest:

"The panels can be opened for maintenance work. The bolts prevent the mechanism from moving upward on rollers when the plane is in flight."

The NTSB did not conclusively say if the bolts came out or were missing, but if the bolts are not in place, the door plug could conceivably pop open and slide up.

The 737-9 that left Portland suffered a violent decompression of the cabin, but no one was injured. The interior suffered extensive damage near the door, but landed safely, The door plug panel was found in the backyard of a home south of Portland.

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The 737s remain grounded, at least with United and Alaska, pending further inspections and investigations.

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