Boeing's stock keeps falling after revelations about internal concern over a flight system tied to two deadly crashes.
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. The pilot told a co-worker he struggled to handle a system called MCAS in a flight simulator and "unknowingly" lied to regulators.
MCAS triggered a nose-down pitch of the planes before accidents in Indonesia and Ethiopia that killed 346 people.
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 shares fell $11.99, or 3.5%, to $332.01 in midday trading after dropping 6.8% Friday.