American Airlines (AA) pilots angrily confronted a Boeing official about an anti-stall system suspected in two fatal crashes of the manufacturer’s 737 Max aircraft, according to a new recording.

In audio obtained by CBS News, members of AA’s pilots’ union quizzed Boeing officials about the system – knowns as MCAS – in a tense meeting in November last year, weeks after a Lion Air Max crashed in Indonesia and four months before the loss of an Ethiopian Airlines Max. In total, 346 people died in the two crashes.

Boeing has been criticized for not disclosing how the MCAS anti-stall system worked – a move that allowed the company to avoid costly retraining.

“We flat-out deserve to know what is on our airplanes,” one pilot is heard saying in the recording.

“These guys didn’t even know the damn system was on the airplane – nor did anybody else,” another said.

The official, Boeing vice-president Mike Sinnett, claimed the Lion Air disaster was a once-in-a-lifetime accident.

He said: “I don’t know that understanding this system would’ve changed the outcome on this. In a million miles, you’re going to maybe fly this airplane, maybe once you’re going to see this, ever. So we try not to overload the crews with information that’s unnecessary so they actually know the information we believe is important.”

The pilots countered: “We’re the last line of defence to being in that smoking hole, and we need the knowledge.”

Boeing said it would make software changes but did not want to “rush and do crappy job of fixing the right things”. The fix was still being developed when the Ethiopian Airlines jet went down.

The release of the recording came as the House transportation committee opened a hearing into the role of Boeing’s regulator, the Federal Aviation Administration (FAA), in certifying the Max.

Democrat Rick Larsen, a member of the committee and the chair of the aviation subcommittee, said: “The FAA has a credibility problem.” He cited a Wall Street Journal story that claimed an internal review had found that senior FAA officials did not participate in or monitor crucial safety assessments of MCAS.

Larsen said: “If that is in fact true, the [designation] process is not working as Congress intended.”

The acting FAA administrator, Daniel Elwell, said he was “not aware of an internal assessment that reaches that conclusion”.

Elwell was criticized for the FAA’s decision to hold off on grounding the US’s Max fleet after the second crash. The FAA was the last major world regulator to ground the plane and did so only after Donald Trump announced that the plane would be grounded.

Democratic congresswoman Eleanor Holmes Norton said: “Why did it take so long compared to other countries? The public wants to know: why did it take so long?”

Elwell said the FAA was a “data-driven, risk based system” and acted after it had received sufficient data to link the two crashes.