The head of the National Transportation Safety Board says Boeing has refused to tell investigators who worked on the door plug that came off a jet midflight in January.
Jennifer Homen disclosed the information during testimony at a Senate committee hearing on Wednesday.
Sen. Ted Cruz asked her whether all of the parties had been forthcoming with information regarding the NTSB's investigation into the incident on Alaska Airlines Flight 1282.
"Boeing has not provided us with the documents and information that we have requested numerous times over the past few months," Homen told Cruz.
She says investigators still don't know who opened the door plug that later blew off the 737 MAX 9 on Jan. 5.
Homen testified that the company has not even confirmed if it keeps records.
"It's absurd that two months later we don't have that," Homen said. "Without that information, that raises concerns about quality assurance, quality management, safety management systems" at Boeing.
"That is utterly unacceptable," said Cruz, R-Texas, responded.
Boeing did not immediately respond to the Associated Press for a request for comment.
Sen. Maria Cantwell, D-Wash., said she will ask Boeing to cooperate with the NTSB investigation, according to the AP.
Cantwell, who represents the state where Max jetliners are assembled, noted that the company is a leading U.S. exporter and major defense contractor.
