Messages from 2016 reportedly show that a Boeing pilot working on the 737 Max warned that the new automated system was making the plane hard to control during flight simulations.
Reuters reported Friday that the company turned over messages from two employees that suggest the airplane-maker may have misled federal authorities about the safety system.
“It’s running rampant in the sim,” a pilot wrote in a message to a colleague, referencing the simulator, according to The New York Times. The pilot added that while he wasn't great at flying, the system was "egregious."
Boeing 737 Max planes had crashed twice in five months — in October 2018 and March 2019 — killing 346 people in the process.
The aircraft has been grounded since March, and the Federal Aviation Administration (FAA) reiterated on Friday that there is no “prescribed timeline, for returning the Boeing 737 MAX to passenger service.”
The FAA said in a statement that Boeing alerted the Department of Transportation to the existence of the new messages on Thursday but that the company "had discovered this document some months ago."
The Department of Transportation brought the document to the attention of the FAA and the department's inspector general, the aviation agency said.
FAA Administrator Stephen Dickson wrote a letter to Boeing chief executive Dennis Muilenburg on Friday demanding answers on why the document wasn't turned over sooner.
"I understand that Boeing discovered the document in its files months ago. I expect your explanation immediately regarding the content of this document and Boeing’s delay in disclosing the document to its safety regulator,” Dickson wrote.
Muilenburg is scheduled to testify about the crashes in front of lawmakers later this month.
"Over the past several months, Boeing has been voluntarily cooperating with the House Transportation & Infrastructure Committee’s investigation into the 737 MAX," a Boeing spokesman told The Hill in a statement Friday.
"As part of that cooperation, today we brought to the Committee’s attention a document containing statements by a former Boeing employee. We will continue to cooperate with the Committee as it continues its investigation. And we will continue to follow the direction of the FAA and other global regulators, as we work to safely return the 737 MAX to service."