Two U.S. pilots’ unions say the potential risks of a safety feature on Boeing Co.’s 737 Max aircraft that has been linked to a deadly crash in Indonesia weren’t sufficiently spelled out in their manuals or training.

In the days since Boeing and the Federal Aviation Administration issued directives last week telling flight crews about the new system, pilots, unions and training departments realized that none of the documentation for the Max family of aircraft included an explanation of the system.

“We don’t like that we weren’t notified,” said Jon Weaks, president of the Southwest Airlines Pilots Association. “The companies and the pilots should have been informed. It makes us question, ‘Is that everything, guys?’ I would hope there are no more surprises out there.”

Dennis Tajer, a 737 captain and spokesman for the Allied Pilots Association at American Airlines, said the union’s members were also concerned.

“This is not about silos and layers of bureaucracy, this is about knowing your airplane,” Tajer said. “We will always be eager and aggressive in gaining any knowledge of new aircraft.”

Few details have been released about underlying causes of the Lion Air crash Oct. 29 in the sea near Jakarta, but Indonesian investigators say that an erroneous sensor on the plane prompted its computers to push the plane into a steep dive. A new safety measure added on the Max models to prevent pilots from losing control is what caused the plane to point downward, according to the FAA and Boeing.

Boeing and the FAA said in the directives that an existing procedure could have halted the dive. The FAA ordered airlines to add an explanation into flight manuals.

Boeing didn’t immediately respond to a request for comment.

–With assistance from Julie Johnsson.

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Photo Credit: The American Airlines pilot union said it was not warned of a possible issue with automation on the new Boeing 737 Max before a jet crashed last month in Indonesia. Boeing