By David Shepardson
WASHINGTON (Reuters) - The Air Line Pilots Association told U.S. safety regulators on Thursday the union was concerned about "a potential, significant aviation system safety deficiency" in the Boeing 737 MAX aircraft, one of which crashed last month in Indonesia.
Boeing Co <BA.N> and the U.S. Federal Aviation Administration issued guidance about the 737 Max's aviation system last week after a Lion Air jet crashed in Indonesia on Oct. 29, killing all 189 people on board.
But the pilots union's president, Tim Canoll, said in a letter to the FAA and National Transportation Safety Board made public on Thursday that "the lack of critical safety information being provided to the air carriers and frontline operators is concerning."
Boeing, asked for comment on the letter, said it was "taking every measure to fully understand all aspects of this incident, working closely with the investigating team and all regulatory authorities involved." The company added that it was "confident in the safety of the 737 MAX."
ALPA, the largest U.S. pilots union, represents 61,000 pilots at 34 airlines in the United States and Canada. Its letter said that it wants agencies working with Boeing "to communicate all relevant information to the operators to ensure the continued safe operation of this aircraft."
In its airworthiness directive last week, the FAA warned airlines that erroneous inputs from the aviation system's sensors could lead the Boeing 737 MAX to automatically pitch its nose down even when autopilot is turned off, making it difficult for pilots to control the jet.
The system was designed to prevent the jet from stalling, according to information provided by Boeing to airlines.
"Based on recent reporting about the 737 Max, we are concerned that a potential, significant aviation system safety deficiency exists, and we are writing to ask for your immediate help and assistance in clarifying the issues with respect to the pitch control system of the aircraft," the union letter said.
Indonesian investigators said on Monday the situation the crew of the doomed Lion Air jet was believed to have faced was not addressed in the aircraft's flight manual. U.S. pilot unions were also not aware of potential risks, two pilot unions previously told Reuters.
In its letter, ALPA said that information about "this system was not provided to the frontline airline employees—the flight crews and maintenance technicians" and it "appears to be a significant information gap."
The FAA did not comment on the letter but said it "will take further appropriate actions depending on the results of the investigation."
The agency said earlier this week that the "FAA and Boeing continue to evaluate the need for software and/or other design changes to the aircraft including operating procedures and training as we learn more from the ongoing investigation."
(Reporting by David Shepardson; Editing by Tom Brown)