The head of the US Federal Aviation Administration has faced another grilling in Congress following revelations that pilots complained to Boeing about the 737 MAX aircraft in the aftermath of a deadly crash last year.
The hearing comes on the heels of a near-constant trickle of news reports in recent weeks that have raised pointed questions about both Boeing and the FAA over an aircraft that has been grounded globally following the second of two deadly crashes in March that led to 346 deaths.
News reports on the eve of the hearing chronicled a 27 November meeting, which came after the Lion Air crash in Indonesia, at which American Airlines pilots pressed Boeing for safety changes that could have temporarily grounded the plane.
Another report yesterday said the FAA did not independently evaluate the safety of a Boeing 737 MAX system implicated in the two deadly crashes, deferring to Boeing on key judgments.
Representative Rick Larsen, a Washington Democrat who chaired the hearing, said he would press for answers to ensure safety.
"The Committee's investigation is just getting started, and it will take some time to get answers, but one thing is clear right now: the FAA has a credibility problem," Larsen said.
"The FAA needs to fix its credibility problem."
Acting FAA Administrator Daniel Elwell, in opening remarks, defended the agency's longstanding practice of designating Boeing and other companies with key roles in certification.
"This is not self-certification," Mr Elwell said.
"The FAA retains strict oversight authority. The program allows the FAA to leverage its resources and technical expertise while holding the applicant accountable for compliance."
A common link in both crashes was the Maneuvering Characteristics Augmentation System.
In both crashes, the MCAS pointed the plane sharply downward based on a faulty sensor reading, hindering pilot control after takeoff, according to preliminary crash investigations.
Reports in the New York Times and the Dallas Morning News recounted the November meeting at which pilots complained about MCAS, which pilots have complained was not in the 737 MAX training material.
"These guys didn't even know the system was on the airplane, nor did anybody else," said Mike Michaelis, head of safety for the pilot's union, according to the New York Times, which reviewed a tape of the meeting.
A Boeing executive at the meeting defended the plane.
"No one has yet to conclude that the sole cause of this was this function on the airplane," Boeing vice-president Mike Sinnett told the meeting.
"The worst thing that can ever happen is a tragedy like this, and the even worse thing would be another one," he said later in the meeting held four months before the Ethiopian Airlines disaster.
The Allied Pilots Association, which represents American Airlines pilots, tweeted a Dallas Morning News article on the meeting.
"Boeing did not treat the 737 MAX situation like an emergency at the time of the November meeting with the Allied Pilots," the organization said.
The hearing comes as the FAA oversees Boeing's upgrade to MCAS as the actions of both the FAA and Boeing are being investigated by government authorities, including the US Department of Justice.
Major US carriers have said they expect to resume flights on the 737 MAX in August, but that timeframe is contingent on FAA approval of the upgrade.
The FAA has called a 23 May meeting of international civil air regulators to Texas to discuss the FAA's process for clearing the 737 MAX to resume service.
"We remain confident that the impending software updates, along with the new training elements Boeing is developing for the MAX, will lead to recertification of the aircraft soon," said an American Airlines spokesman.
"Our team continues to work collaboratively with the FAA, Boeing and the Allied Pilots Association in this process."