Retired Boeing senior manager Ed Pierson on Wednesday raised the alarm in Congress about the Renton plant where the 737 MAX is built.
"I believe production problems at the Renton factory may have contributed to these two fatal crashes," Pierson said.
Pierson said schedule pressure led to long work hours and assembly done out of sequence because parts arrived late.
Pierson said he was so concerned about mistakes, he even asked a Boeing leader to temporarily shut down the line.
“When I mentioned that I’ve seen operations in the military shut down for lesser safety concerns, I will never forget his response, which was the military isn’t a profit-making organization,” Pierson said.
“During this time, the 737 factory was in chaos. Every single health metric was getting record low marks and everyone was trending in the wrong direction.”
In an email, Boeing called Pierson's suggestion of a link between production problems and the crashes "completely unfounded" and "inconsistent with the facts" found by investigators.
Also on Wednesday, House committee chair Peter DeFazio of Oregon pointed to an FAA analysis after the first MAX crash that problems with the stall-prevention system could lead to 15 more crashes over the life of the fleet if not corrected.
"Despite its own calculations, the FAA rolled the dice on the safety of the traveling public and let the 737 MAX continue to fly until Boeing could overhaul its MCAS software," DeFazio said.
The planes were grounded after the second crash.
On Wednesday, FAA Administrator Steve Dickson again signaled that regulators won’t rush to return the MAX to the sky.
"The FAA fully controls the approvals process and is not delegating anything to Boeing," Dickson said.
Before the hearing, Dickson told CNBC recertification would not happen before the end of 2019, as Boeing had been hoping.