Former Boeing 737 MAX Chief Technical Pilot Charged With Hiding Design Changes

WASHINGTON—A U.S. federal grand jury has indicted former Boeing 737 MAX chief technical pilot Mark Forkner, alleging he intentionally withheld crucial information about flight control software changes from FAA officials during the model’s certification, helping set the stage for two fatal accidents linked to the software.

The indictment, announced Oct. 14 by the U.S. Justice Department (DOJ), charged Forkner with two counts of fraud involving aircraft parts in interstate commerce, for knowingly sending false information—737 MAX training documents—to American Airlines and Southwest Airlines in 2017, and four counts of wire fraud linked to electronic invoices Boeing sent the airlines as part of their orders.

The case’s lead investigators, the Federal Bureau of Investigation’s Chicago field offices and the U.S. Transportation Department’s Office of Inspector General, built their indictment around how Forkner handled information about the maneuvering characteristics augmentation system (MCAS) software that Boeing added to the 737 MAX.

The MCAS, which automatically adjusts the horizontal stabilizer based on angle-of-attack (AOA) data, was added to the 737’s speed trim system (STS) to ensure the MAX feels just like its predecessor, the 737NG, to pilots during certain, rare flight profiles. The MCAS’s original authority only covered high-speed scenarios not normally experienced during routine operations but must be demonstrated during certification. 

Forkner, who became the 737 MAX chief technical pilot in early 2014, knew this, and communicated it to officials within the FAA’s Aircraft Evaluation Group (AEG) multiple times, including during a June 2015 meeting, the indictment said.

Boeing began flight testing the 737 MAX in January 2016. Boeing soon determined that MCAS’s authority needed to be expanded to some low-speed scenarios. The MCAS’s original, high-speed-scenario configuration triggered a maximum of .65 deg. of stabilizer movement per activation. In March 2016, MCAS Revision D was released. The new, low-speed functionality required more stabilizer movement—2.5 deg.—per activation to achieve the required results. The MAX’s stabilizer ranges from maximums of 4.2 deg. aircraft nose down to 12.9 deg. aircraft nose up.

Revision D included an updated functional hazard assessment that analyzed possible failure scenarios. One was an uncommanded or unneeded MCAS activation that would trigger multiple, repeated nose-down commands. Boeing assumed pilots would categorize the failure as a common runaway stabilizer and react within 4 sec. by toggling switches to disconnect the stabilizer from the motor that drives it, leaving pilots with a hand-cranked wheel to adjust the flight-control surface. The hazard assessment noted that failure to react within 10 sec. would create a “catastrophic” scenario, leaving pilots unable to recover.

While some in the FAA, including flight-test engineers, were told about the MCAS changes, Boeing did not—and was not required to—provide the revised MCAS specifications to the AEG or FAA certification engineers. It also did not update the broader horizontal stabilizer system safety assessment (SSA) that included MCAS beyond Revision C changes.

Forkner was not told about the changes either.

At the same time Revision D was being developed, Forkner was pushing to have all references to MCAS removed from pilot training manuals—part of a focused effort to ensure 737 pilots could transition to the newest variant without costly, time-consuming simulator sessions. This required keeping the 737 Next Generation and 737 MAX as similar as possible. With this in mind, Boeing attempted to design MCAS to be transparent to pilots, reasoning they would recognize an MCAS-related malfunction as a common runaway stabilizer issue.

In a March 30, 2016 e-mail released as part of a Congressional probe into the 737 MAX certification, Forkner asked an unidentified FAA staff member about removing “all reference to MCAS” from the flight crew operations manual “as we discussed, as it’s completely transparent to the flight crew and only operates way outside of the normal operating envelope.” 

Several months later, Forkner learned about the Revision D changes firsthand. In November 2016, Forkner flew the 737 MAX simulator and “experienced MCAS operating at a significantly lower speed (Mach 0.2) than what [he] and Boeing had previously told the FAA AEG,” the indictment said. He then consulted with a Boeing engineer, who confirmed the changes included in Revision D.

Forkner never told the AEG what he learned, the indictment alleges, pointing to a meeting soon after the simulator session as an example of willful neglect.

“During this meeting, FAA AEG Employee-I asked Forkner about his experience in the simulated test flight,” the indictment said. “In this conversation, Forkner withheld from FAA AEG Employee-I the material fact that MCAS could now operate during nearly the entire speed range for the 737 MAX, including at speeds as low as Mach 0.2.”

Meanwhile, Forkner kept pushing the FAA to permit Boeing to drop MCAS from the aircraft’s flight manuals and related documentation, the indictment described. Days after the simulator session and FAA meeting, Forkner received a copy of the draft Flight Standardization Board (FSB) report detailing minimum training for 737 MAX pilots, including differences from previous versions of the aircraft. It included several references to MCAS. Forkner lobbied the agency to have them removed, citing conversations that started before the Revision D changes. 

“[W]e agreed to not reference MCAS since it’s outside [the] normal operating envelope,” one message from Forkner to the FAA said, according to the indictment. “This representation was materially false because Forkner knew that the FAA AEG had ‘agreed to not reference MCAS’ based on outdated and incorrect information that MCAS was designed to operate during high-speed, wind-up turns,” the indictment added. “At the same time that he proposed that the FAA AEG delete MCAS from the 737 MAX FSB report, Forkner withheld the true, accurate, and complete information about MCAS ‘s low-speed expansion.” 

The FAA certified the 737 MAX 8 on March 8, 2017. The final FSB released to support the certification did not mention the MCAS.

“In an attempt to save Boeing money, Forkner allegedly withheld critical information from regulators,” Acting U.S. Attorney Chad E. Meacham for the Northern District of Texas said. “His callous choice to mislead the FAA hampered the agency’s ability to protect the flying public and left pilots in the lurch, lacking information about certain 737 MAX flight controls.”

Faulty assumptions and mistakes made during the MCAS’s design and approval, including pilots’ and FAA engineers’ lack of knowledge of the system, were flagged by investigators as factors in two fatal 737 MAX 8 accidents: Lion Air Flight 610 in October 2018 and Ethiopian Airlines Flight 302 in March 2019. 

In both cases, the MCAS activated based on faulty AOA data that told the aircraft’s flight control software its nose was too high just after takeoff. Neither crew reacted as Boeing’s hazard assessment anticipated, and both aircraft crashed after uncontrollable dives triggered by repeated MCAS activations. 

Investigators determined the FAA AEG did not learn about the expanded MCAS authority until after the Lion Air accident. 

The accidents killed all 346 people onboard, led to the worldwide grounding of the 387-aircraft 737 MAX fleet in March 2019, and prompted regulators to order changes to the MCAS and pilot training. The aircraft returned to service in December 2020.

The accidents also triggered reviews of how the FAA certifies aircraft and how Boeing develops them. The FAA is implementing changes to its certification process, including some mandated by a December 2020 law.

Boeing and the DOJ reached a settlement earlier in 2021 over criminal charges against two former employees, including Forkner.