U.S. air safety officials have been defending their record over two deadly Boeing crashes.

They reassured lawmakers they’ll allow the 737 Max jet to resume flying only when it’s safe to fly again.

But there’s growing anger about the approach both Boeing and safety officials took, as CGTN’s Owen Fairclough reports.

The acting head of the U.S. Federal Aviation Administration appeared before Congress on Wednesday determined to restore faith in its safety checks.

“We will not allow the 737 Max to fly in the US until it is absolutely safe to do so, and we will use every tool every data gathering ability we have to ensure that’s the case,” Daniel Elwell, the Acting Administrator of Federal Aviation Administration said.

Elwell testifying before the House Committee on Transportation and Infrastructure after two Boeing 737 Max crashes in Indonesia last October and Ethiopia in March claimed 346 lives and led to the jet’s grounding worldwide.

But his reassurance wasn’t enough for lawmakers who want to know why the FAA signed off on anti-stall software blamed for forcing the jets into uncontrollable nosedives.

Committee Chairman Peter DeFazio asked Elwell: “How did that get certified? How can we have a single point of failure on a modern aircraft? How can you have a critical safety system certified?”

Boeing is equally under fire — partly because it knew about problems with the software more than a year before informing the FAA.

Elwell told the committee: “It languished and I am not happy with a 13-month gap between finding that anomaly and us finding out about it.”

In a secretly-taped meeting with Boeing, American Airlines pilots confronted the airline after the Indonesia crash, demanding software fixes and more training for the 737 Max.

Congressman Colin Allred asked Elwell: “The pilots expressed a number of concerns to the Boeing executives and my question to you is was the FAA made aware by Boeing or by anyone else about that meeting about any of the pilots’ concerns?”

“I don’t discount what was reported in that meeting and I don’t discount it from an air safety perspective,” Elwell replied.

Boeing did not testify at the hearing. It said in a statement that its longstanding collaboration with the FAA has created the safest transportation system in the world.