The Society of Professional Engineering Employees in Aerospace (SPEEA), a union representing Boeing engineers, filed a complaint with the National Labor Relations Board (NLRB) on Tuesday (Apr. 23) on behalf of one of the two engineers seeking to uncover a report from Boeing's internal investigation into the incident filed with the Federal Aviation Administration (FAA). 

According to CNN, the union alleged the already embattled aviation company retaliated against the two engineers, who were working with the FAA to provide manufacturing insight.

SPEEA said in a press release, also released Tuesday, that the two workers "insisted the company reevaluate prior engineering work on the 777 and 787 to account for a new FAA advisory" in 2022. 

The company initially dismissed recommendations to redo the work before agreeing to do it, but then retaliated against the two in their performance reviews, the union said, adding that they were only representing one of the two engineers since the second worker has since "quit Boeing over the way he was treated."

Boeing responded that the investigation was part of a confidential process and that the report could only be shared with the FAA.

"We have zero tolerance for retaliation and encourage our employees to speak up when they see an issue," Boeing said in a statement. "After an extensive review of documentation and interviewing more than a dozen witnesses, our investigators found no evidence of retaliation or interference. We have determined the allegations are unsubstantiated."

Meanwhile, Boeing whistleblower Sam Salehpour told Congress last week that he had concerns about the way Boeing was consolidating and fusing fuselages on the 787 and 777 models and that he had faced retaliation for raising such concerns.

The FAA said that it was investigating the matter.