Boeing’s (BA.N), opens new tab safety culture and manufacturing quality, both at the center of a corporate crisis following a January mid-air panel blowout on a near-new 737 MAX 9, were scrutinized on Wednesday in two U.S. Senate hearings.

During the hearing on Wednesday, whistleblower Sam Salehpour, a Boeing quality engineer who raised questions about two of its widebody jets, claimed he was told to “shut up” when he flagged safety concerns. He has said that he was removed from the 787 program and transferred to the 777 jet due to his questions.

U.S. Senate Commerce Committee Chair Maria Cantwell said she expects Boeing to submit a serious plan in response to a FAA deadline. In late February, the FAA said Boeing must develop a comprehensive plan to address “systemic quality-control issues” within 90 days.