Boeing executives have sought to assuage concerns of pilot groups and customers in the weeks since a new Boeing 737 Max 8 crashed off the coast of Indonesia, even as an investigation into the cause of the crash remains inconclusive.

In an internal memo sent to employees last week, Boeing chief executive Dennis Muilenburg reiterated the safety record of the company’s 737 commercial jetliner, which he described as “a safe airplane designed, built and supported by skilled men and women who approach their work with the utmost integrity.”

He pledged to continue to improve safety processes. “Regardless of the outcome, we’re going to learn from this accident and continue to improve our safety record,” Muilenburg wrote.

The company is grappling with the fallout of an Oct. 29 disaster in which a Boeing 737 Max 8 operated by Indonesian budget airline Lion Air crashed into the Java Sea shortly after takeoff from Jakarta, killing all 189 people on board.

Pilot groups have said they were “kept in the dark” about an update to the plane’s automated safety system. The Boeing 737 has gone through multiple iterations and upgrades since it first flew in 1967. Its newest model is the 737 Max.

When Boeing repositioned the engines on the Max and made them more powerful, it introduced a system called MCAS (Maneuvering Characteristics Augmentation System) that was intended to make the airplane behave identical to its predecessor, the 737 Next Generation. Given that intention, Boeing told the airlines about MCAS, but pilots say it wasn’t included in their training.

It remains unclear whether Lion Air’s 737 operated as Boeing expected it would. Boeing notified pilots in a Nov. 6 advisory that a manual override feature of earlier 737 models would not work on the Max 8, but Boeing representatives have not answered questions about when the company first became aware of that change. It’s also unclear why it was not addressed in pilot training.

“Listening to pilots is a critical part of our work,” a Boeing spokeswoman said. “Their experienced input is front-and-center in our mind when we develop airplanes.”

The 737 in the Lion Air crash had experienced a problem on the flight into Jakarta in which the displays for the pilot and the co-pilot showed different information, according to a preliminary report released this week by Indonesian investigators. That problem on the day before the fatal flight was addressed by engineers overnight, but apparently wasn’t resolved.

After the Lion Air crash, Boeing issued a bulletin to airlines that said faulty airspeed indicators could “trim the stabilizer nose down in increments lasting up to 10 seconds.” Though the investigation is ongoing, it appears the pilots on the doomed flight were fighting the MCAS, which interpreted faulty input from an airspeed indicator to mean the plane was in a stall from which it might not recover unless immediate action was taken. The MCAS responded by directing the nose down.

“Does this mean the MCAS and other flight programs are unable to resolve discrepancies between the left and right seat flight displays, and isn’t that a terrible design flaw?” said Mary Schiavo, an aviation lawyer and former inspector general of the U.S. Transportation Department. “The computer can’t reconcile the difference, or permit the [co-pilot] to fly normally from the right seat when there is a problem” with the pilot’s control display.

A preliminary report released Wednesday by the Indonesian National Transportation Safety Committee (NTSC) detailed the chaotic final minutes of the flight. According to the report, pilots fought to keep the plane level as it repeatedly steered toward the sea.

It is not clear whether the pilots attempted a “runaway stabilizer” procedure that would have overridden the plane’s automated system. Black box data released by investigators showed pilots were pulling back on the control column in an attempt to raise the plane’s nose, applying almost 100 pounds of pressure to it.

The report stopped short of assigning blame for the crash. A summary presented to reporters Wednesday by the NTSC noted that the report had recommended Lion Air “improve the safety culture” while also “ensuring that all operation documents are properly filled and documented.”

Muilenburg referred to the crash as “a tragic accident.” He said Boeing’s employees have been “pouring significant energy into actively supporting the investigation and our MAX customers.”

A Boeing spokeswoman said Thursday that the company regularly communicates with airlines and pilots but has “stepped up that engagement” in recent weeks, including “reinforcement of appropriate existing procedures” relevant to the situation investigators have described in Lion Air Flight 610.

“Every day, millions of people rely on our commercial airplanes to crisscross the globe safely and reliably,” Muilenburg told employees. “When that doesn’t happen, for any reason, we take it seriously.”

Pilot union representatives say they have met with Boeing technical experts about the 737 safety features.

Allied Pilots Association communications committee chairman Dennis Tajer said a group of Boeing representatives, including a high-level engineer and a company test pilot, met with APA pilots at the association’s headquarters in Fort Worth on Tuesday. Jon Weaks, president of the Southwest Airlines Pilots Association, said the company held a similar meeting in Reno, Nev., on Sunday. A Boeing representative declined to comment on the meetings.

“As far as I know, it was the first time that a manufacturer had reached out to SWAPA directly,” Weaks said. “We appreciated it, and we were disappointed we didn’t know about MCAS before, but at a certain point you have to move forward.”

Also in the memo to employees, Muilenburg asserted that the company had not withheld information from customers.

“You may have seen media reports that we intentionally withheld information about airplane functionality from our customers. That’s simply untrue,” Muilenburg wrote. “The relevant function is described in the Flight Crew Operations Manual, and we routinely engage customers about how to operate our airplanes safely.”

Customers and their passengers, a Boeing spokeswoman said, “have our assurance that the 737 Max is as safe as any airplane that has ever flown the skies.”