Boeing manufacturing practices and production lines under investigation

The Federal Aviation Administration (FAA) is now investigating Boeing's manufacturing practices and production lines, the agency announced Wednesday.

The FAA previously said it was inspecting all Boeing 737-9 MAXs before they return to service. While the first 40 inspections are now complete, the FAA is still reviewing the data from the planes.

The investigation comes nearly two weeks after the Max 9 mid-flight blowout on Jan. 5. that happened during an Alaska Airlines flight headed from Portland to Ontario, California.

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All 737-9 MAX aircraft with door plugs will remain grounded pending the FAA’s final approval of its inspection. Every grounded 737-9 MAX will have to undergo an inspection and maintenance process before they return to the skies.

The FAA says the safety of the flying public will determine the timeline for the Max 9's return to service.

The FAA also supports the National Transportation Safety Board's (NTSB) investigation into Alaska Airlines Flight 1282. The NTSB is providing all future updates on the investigation.

READ: US intensifies oversight of Boeing, will begin production audits after latest mishap for planemaker