Boeing Co. said it told U.S. regulators “multiple times” that it had expanded the role of flight-control software later linked to two fatal crashes, and that Federal Aviation Administration personnel observed the system operating in flight tests before the 737 Max was certified for service.

The statement, posted online Sunday, provided a broader explanation to last week’s bombshell revelation that a former senior Boeing pilot had described the Maneuvering Characteristics Augmentation System, also known as MCAS, as “egregious” to a colleague. In an instant-message exchange after a rocky simulator run in August 2016, Mark Forkner, now a Southwest Airlines pilot, said he had unknowingly “lied” to the FAA about its behavior.

The latest controversy swirling around the grounded 737 Max adds to the pressure on the planemaker and Chief Executive Officer Dennis Muilenburg as directors and senior executives gather in San Antonio, Texas, for a regularly scheduled board meeting Sunday evening and Monday. Delays in getting approval to return the plane to service have cost Boeing at least $8.4 billion and Muilenburg his post as chairman.

The FAA said in an email Sunday that it would stand by comments it released Oct. 18, when it called the pilot’s comments “concerning” and chastised Boeing for not revealing the information sooner. “The FAA is reviewing this information to determine what action is appropriate,” the U.S. regulator said.

Public Rift

The public rupture comes as Boeing and the regulator are working to get the 737 Max back into the skies and rebuild public trust after months of bruising publicity. The commercial return of Boeing’s best-selling plane has slipped repeatedly and now isn’t likely before 2020.

“We understand and regret the concern caused by the release” of the instant messages, Boeing said. “It is unfortunate that this document, which was provided early this year to government investigators, could not be released in a manner that would have allowed for meaningful explanation.”

Boeing’s statement on Sunday expands on the company’s long-standing position that it was transparent with FAA about MCAS and believed it to be safe.

“Boeing engaged in an extensive process with the FAA to determine pilot training requirements for the 737 MAX 8,” the company said in the statement. “This process was a complex, multiyear effort that involved a large number of individuals at both Boeing and the FAA. This effort itself was just a part of a much larger regulatory process for the design, development and certification of the 737 MAX 8.”

MCAS Design

MCAS is a safety feature designed to automatically push down a plane’s nose in some cases when the plane gets close to an aerodynamic stall. Two crashes within less than five months—Lion Air Flight 610 on Oct. 29 off the coast of Indonesia and Ethiopian Airlines Flight 302 on March 10—killed 346 people, and indications are that malfunctions triggered MCAS to repeatedly push the planes’ noses down until pilots lost control.

One of the concerns being raised about how MCAS was approved revolves around changes to the cirucmstances under which it activates, and whether those were fully explained to the FAA and other nations. The system had originally been designed to address potential stalls at high speeds only, but during flight-testing was expanded to activate with slower speeds.

Boeing briefed the FAA and international regulators “on multiple occasions,” the statement said. Flight-test aircraft were equipped with the expanded version of MCAS and FAA personnel observed how the system operated during flight testing from August 2016 through January 2017, it said.

The planemaker said it has been unable to speak to Forkner to gain context on exactly what he meant in those 2016 instant messages. The pilot’s attorney says his client wasn’t hiding anything and that based on everything Forkner knew at the time, “he absolutely thought this plane was safe.”

Test Pilot

“If you read the whole chat, it is obvious that there was no ‘lie,’” David Gerger, Forkner’s lawyer, said in an email. “The simulator was not reading right and had to be fixed to fly like the real plane.”

Forkner, who was Boeing’s chief technical pilot for the 737 Max at the time, was part of a group of pilots working on the flight crew operations manual and ensuring that flight simulators closely mirrored the behavior of the aircraft.

In the messages, Forkner and Gustavsson raised concerns about MCAS, including not being given data by the company’s test pilots. Forkner, describing his alarm at simulator tests in which he encountered troubling behavior in the system, told his colleague that MCAS was “running rampant in the sim on me,” referring to simulator tests of the aircraft. “Granted, I suck at flying, but even this was egregious.”

Forkner expressed concern that he may have unknowingly misled the FAA. “So I basically lied to the regulators (unknowingly),” he wrote.

“It wasn’t a lie, no one told us this was the case,” Gustavsson replied.