Boeing's chief executive told lawmakers on 29 October that he was unaware until recently of newly-disclosed instant messages in which Boeing's former chief technical pilot described concern about the function of the 737 Max's Maneuvering Characteristics Augmentation System (MCAS) and said he unknowingly lied to regulators.
"I became familiar with the details of the documents over the last few weeks, and we expressed our disappointment and concern [about] how this came to the FAA," Boeing CEO Dennis Muilenburg said during a 29 October hearing before the Senate Committee on Commerce, Science and Transportation.
During the same hearing, Boeing chief engineer John Hamilton also conceded shortcomings in assessments Boeing made of the MCAS system during its development.
"Yes, in hindsight," Hamilton said when asked if Boeing's MCAS hazard assessment had been faulty.
Muilenburg and Hamilton testified for several hours before the Senate committee, which has been investigating the development, certification and safety of the 737 Max. Regulators grounded the jet in March following two crashes that killed 346 people.
Muilenburg and Hamilton are scheduled to testify about the same topic tomorrow before the House Committee on Transportation and Infrastructure.
During the Senate hearing, lawmakers repeatedly asked Muilenburg when he first learned of MCAS-related instant messages and emails sent in 2016 and 2017 by Boeing's former chief 737 technical pilot Mark Forkner, who worked on the 737 Max's certification.
In November 2016, Forkner sent instant messages to another Boeing staffer in which described MCAS as "running rampant in the sim", and "egregious".
"So I basically lied to the regulators (unknowingly)," Forkner wrote in the messages, released by the House transportation committee.
In 2017, Forkner sent emails to Federal Aviation Administration (FAA) certification staffers requesting that mention of MCAS be removed from 737 Max training materials, a change the FAA ultimately approved. In emails, Forkner described his efforts to convince officials to certify the 737 Max's pilot training as "Jedi mind-tricking regulators".
Indonesian accident investigators have concluded a lack of pilot knowledge about MCAS was among many factors contributing to the October 2018 crash of a Lion Air 737 Max 8.
Forkner no longer works at Boeing.
Boeing has since said Forkner's lawyers have told them the emails "reflected a reaction to a simulator programme that was not functioning properly".
Boeing knew of the text messages months before it delivered them to the US Department of Transportation on 17 October, the FAA has said. That delay prompted FAA administrator Stephen Dickson to write Muilenburg on 18 October, demanding an explanation.
Lawmakers grilled Muilenburg about when he learned about the content of Forkner's messages.
Muilenburg tells senators he was unaware of details in Forkner's messages until they were published in the press earlier this month.
"I was aware of the documents that were being produced as part of the investigation," Muilenburg says. "I counted on our team to make sure all the right authorities were notified."
"I didn't see the details of this exchange until recently. [Forkner's] lawyer suggested he was talking about a simulator in development… That could be the case, we don't know."
Asked about Forkner's mention of "Jedi mind tricking regulators", Muilenburg says, "I'm not sure what he means".
Muilenburg insists Forkner's language is antithetical to Boeing's culture and commitment to safety. "The premise that we would lie and conceal is not consistent with our values," Muilenburg says.
The CEO says Boeing left MCAS out of training manuals because it expected pilots would interpret an MCAS activation as a "runaway stabiliser" – an event correctable via a memorised checklist.
Muilenburg says Boeing's training philosophy aims to ensure pilots can respond to problems without needing to diagnose them, though Boeing now believes pilots should have been made aware of MCAS.
Muilenburg conceded responsibility for some other aspects of the accident, including that 737 Max lacked an angle-of-attack (AOA) "disagree" warning which was supposed to be standard equipment.
Because AOA failures cause MCAS to activate, an AOA disagree warning might have given pilots of the crashed aircraft more information about the nature of the problem they faced.
"We made a mistake in that implementation. The angle-of-attack disagree alert will be standard… on all Maxs going forward," Muilenburg says.
He also repeatedly stressed that Boeing has overhauled its internal structure to improve the company's ability to identify and address safety concerns.