The company which manufactured the door plug which blew out of an Alaska Airlines plane was warned of an 'excessive amount of defects' before the incident.
The Federal Aviation Administration grounded all 171 737 MAX 9 planes operated by US airlines after the door plug blew out mid-air on 5 January.
Pressure dropped on board as a result of the gaping hole, forcing the plane to turn back to the airport in Oregon just six minutes after taking off.
Thankfully the incident didn't prove fatal, but it quickly prompted an investigation and raised questions about how such a large section of the plane could simply disappear.
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Just weeks before Friday's incident, the manufacturer which created the door plug, Spirit AeroSystems, became the focus of a class-action lawsuit claiming it had experienced 'sustained quality failures' in its products.
The lawsuit, submitted in New York on 19 December, was filed on behalf of investors in the company and features claims from employees.
In the suit, investors claim Spirit AeroSystems' problems were 'widespread', and included 'the routine presence of foreign object debris' in products', as well as 'missing fasteners, peeling paint, and poor skin quality'.
"Such constant quality failures resulted in part from Spirit's culture which prioritized production numbers and short-term financial outcomes over product quality," the complaint adds.
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One claim included in the lawsuit was made in an email to one of the company's executives, and spoke of an 'excessive amount of defects'.
The complaint also pointed to two specific manufacturing problems Spirit AeroSystems had allegedly been responsible for, including that it had 'mis-drilled holes on the 737 Max aft pressure bulkhead', at the rear of the plane, and a 'defect relating to the tail fin fittings on certain 737 MAX aircraft'.
The latter issue is one which was flagged by Boeing in April.
None of the issues raised in the lawsuit specifically involve door plugs, but the filing claims Spirit AeroSystems' 'quality failures were so severe and persistent that Boeing even placed Spirit on probation for multiple years'.
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In response to the lawsuit, Spirit AeroSystems told UNILAD: "Spirit strongly disagrees with the assertions made by plaintiffs in the amended complaint and intends to vigorously defend against the claims. Spirit will not comment further as to the pending litigation.”
Boeing has not commented on the lawsuit specifically, but released a statement after the Alaska Airlines incident to say it was 'committed to ensuring every Boeing airplane meets design specifications and the highest safety and quality standards'.