Commercial airline pilots at Southwest and American airlines were not informed during training about a new flight control system that may have played a role in the fatal crash of a Boeing 737 MAX 8 operated by Lion Air in Indonesia last month, pilot union representatives from both airlines said Tuesday.

Jon Weaks, president of the Southwest Airlines Pilots Association, said pilots were not made aware of the issue until last week, when Boeing sent out an advisory over the issue.

“We did not know this was on the [Boeing 737] MAX models,” Weaks said in a Tuesday interview, referring to a new automated flight control feature designed to prevent the plane from stalling by automatically nudging its nose downward in response to externally collected flight data. “When you’re responsible for that aircraft and there are systems on there that you have not been made aware of, that’s not right."

Dennis Tajer, communications committee chairman at Allied Pilots Association (APA), a labor union representing American Airlines pilots, said Boeing exhibited a “failure of the safety culture” by not updating pilots early enough on how the new systems work.

“This was clearly a sign that the safety culture [at Boeing] was missing on a cylinder or two,” he said. “We’re all on the same side looking at Boeing, saying, ‘What else you got?’ ”

In response to the concerns raised by the pilots, a Boeing spokesman said the company is “deeply saddened” by the recent plane crash in Indonesia and is working with officials to determine what went wrong.

“We are taking every measure to fully understand all aspects of this incident, working closely with the investigating team and all regulatory authorities involved,” Boeing spokesman Paul Bergman said. “We are confident in the safety of the 737 MAX. Safety remains our top priority and is a core value for everyone at Boeing.”

Authorities are trying to understand the implications of an Oct. 29 crash near Jakarta, Indonesia, in which a Boeing 737 MAX 8 jet operated by Lion Air crashed into the Java Sea with 189 people on board. A “black box” flight data recorder recovered from the wreckage showed that the plane’s airspeed indicator had malfunctioned on its last four flights.

The exact cause of the crash, however, remains unknown. In the meantime, airlines, pilots, regulators and jet manufacturers have been frantically reviewing flight protocols and systems to ensure passengers on other 737 MAX 8 jets are not put at risk.

Updates issued last week by Boeing and the U.S. Federal Aviation Administration warned airlines that erroneous sensor readings from an important flight control system could “cause the flight crew to have difficulty controlling the airplane,” and lead to “possible impact with terrain.”

A feature in previous 737 models that allowed pilots to manually override an “electric trimming” process – which can automatically nudge the nose of the plane downward in certain situations – does not work in Boeing’s 737 MAX 8 planes, Boeing explained in a Nov. 7 bulletin.

“This is the first description you, as 737 pilots, have seen," APA safety committee chairman Mike Michaelis told pilots Saturday in an advisory note obtained by The Washington Post and reported earlier by the Seattle Times. "It is not in the [flight manuals]. It will be soon.”

Pilots say it is important that they have the power to manually override automated systems. In the case of Lion Air Flight 610, a sensor that measures which way the plane’s nose is pointing apparently fed erroneous data into the system, something that could have sent the plane into a nosedive.

The new flight-control systems “automatically put the nose down to keep the plane from stalling," Mary Schiavo, an airline lawyer and former inspector general of the U.S. Transportation Department, said in an email. “But the pilots don’t know this and are not trained on this. So the pilots keep putting the nose up and the plane keeps putting the nose down.”

Analysts caution against assigning blame before authorities complete their investigation. Still, the response from regulators and pilot representatives hints at a broader reckoning in the commercial aerospace industry over one of Boeing’s marquee jets, the 737 MAX 8.

“There is not any commercial damage to Boeing, but reputationally they need to get ahead of this,” said Richard Aboulafia, an aerospace analyst with Teal Group.