Four flight attendants on the Alaska Airlines 737 MAX 9 plane that experienced a mid-air cabin panel blowout in January last year are suing Boeing for physical and emotional injuries.

In separate lawsuits, they are seeking compensation for past and future economic damages, citing physical and mental injuries, emotional distress and other financial costs.

"Each of the four flight attendants acted courageously, following their training and putting their passengers' safety first while fearing for their lives," said Tracy Brammeier, the attorney representing each of the plaintiffs.

"They deserve to be wholly compensated for this life-altering traumatic experience."

Boeing declined to comment, while Alaska Airlines did not immediately respond to Reuters' request for comment.

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The lawsuits were filed on Tuesday in Seattle's King County Superior Court and accuse Boeing of negligence and failure to exercise reasonable care in the production, sale and repair of 737 MAX jets and its parts.

"Boeing knew or should have known of the quality control issues present in its production of the 737 MAX line of aircraft," the filings said.

The incident sparked a crisis for the planemaker and prompted the U.S. Justice Department to open a criminal investigation into the company and declare that Boeing was not in compliance with a 2021 deferred prosecution agreement.

Last month, the National Transportation Safety Board (NTSB) said Boeing had failed to provide adequate training, guidance and oversight to prevent the incident.

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The board criticized Boeing's safety culture and its failure to install four key bolts in the panel during production, and accused the Federal Aviation Administration (FAA) of ineffective oversight.