The acting head of the Federal Aviation Administration defended the way his agency certifies airline safety after two deadly crashes of the now-grounded Boeing 737 Max jet.
Daniel Elwell called the system in which FAA-approved employees at plane manufacturers inspect the aircraft they built themselves "a good system."
But skeptical Democrats on the House Transportation Committee questioned the agency's credibility.
They told Elwell that the closeness between Boeing and the FAA may be one of the reasons it took the agency a relatively long time to ground the Boeing jets.
"The public perception is you were in bed with those you were supposed to be regulating," Nevada's Dina Titus said, while committee chairman Peter DeFazio wanted to know "How can we have a single point of failure on a modern aircraft?"
A Boeing 737 Max crashed off the coast of Indonesia in October and another 737 Max crashed in Ethiopia in March, killing a total of 346 people.
Both planes were equipped with a system designed to push the nose downward to prevent a midair stall.
Faulty sensor readings kept pushing the planes down while the pilots struggled to regain control.
The pilots did not know the planes were equipped with the anti-stall system and their manuals had no explicit information.
Elwell defended the FAA's approval of the system on the Boeing jets, but admitted the system should have been better explained in the pilots' operational and flight manuals.
He also faulted Boeing for failing to inform airlines and the FAA that a light that is supposed to flash when there is a faulty reading from the sensors did not work.
But Elwell said pilot error may have also contributed to the Indonesian and Ethiopian disasters.
The Justice Department has opened a criminal investigation of Boeing, and Congress is looking into the relationship between Boeing and federal regulators.
Boeing plans to submit changes to the 737 Max software to the FAA, which will study the new software and carry out tests flights. Boeing will train pilots before allowing the planes to fly again.