Boeing's Chief Executive Dennis Muilenburg, but no longer its chairman, is expected to speak with analysts Wednesday on the company's third-quarter results and where it may be heading.
Boeing's stock keeps falling after revelations about internal concern over a flight system tied to two deadly crashes.
The shares fell $12.94, or 3.76 percent, by the market close Monday after dropping 6.8% Friday.
Credit Suisse and UBS downgraded Boeing to "neutral" on Monday, citing Friday's disclosure of a senior Boeing test pilot's messages about the 737 Max.
In the messages, former senior Boeing test pilot Mark Forkner told a co-worker in 2016 he unknowingly misled safety regulators about problems with a flight-control system that would later be implicated in the crashes. Forkner said the new automated flight system, called MCAS, was "egregious" and "running rampant" while he tested it in a flight simulator.
MCAS triggered a nose-down pitch of the planes before accidents in Indonesia and Ethiopia that killed 346 people.
The exchange occurred as Boeing was trying to convince the Federal Aviation Administration the system was safe.
"You just take a look at the FAA administrator's letter Friday, which was terse, it was angry, it was demanding, and that could delay things again," said Scott Hamilton, who tracks the airline business for Leeham and Co. "I think it's possible we could see a rate adjustment on the 737 downward."
Boeing says it's still trying to understand the comments of the test pilot, who now works for Southwest Airlines. Boeing notes the man's lawyer says he was describing problems with a simulator program.
The company said in a statement Sunday it's unfortunate that messages between co-workers it turned over last week weren't released in a manner allowing for "meaningful explanation."
The FAA's administrator on Friday demanded an explanation from Boeing, including why the company delayed telling the agency about the messages for several months.
Boeing said Sunday it's continuing to investigate the circumstances of the exchange but that the simulator software described by Forkner in 2016 was still in testing and had not been finalized. The company said it had briefed both the FAA and international regulators "on multiple occasions" about the final configuration of the flight system.