Boeing chief executive Dennis Muilenburg said Thursday company test pilots have already flown 96 flights totaling 159 hours with an updated software fix installed on the 737 MAX, and will soon also fly production flights, meaning planes being prepped for delivery to customers.

In its campaign to convince both the public and safety regulators worldwide that the MAX can fly safely with the software update, Muilenburg also said the company in the last two weeks held information sessions in the U.K., Singapore and China following a similar meeting last month in Seattle with about 200 airline officials and regulators.

“We want everyone to be confident in it,” he said.

Muilenburg, speaking at a Forum on Leadership at the George W. Bush Presidential Center  in Dallas, also described the impact of the recent 737 MAX crashes on himself and the company.

“All of us feel the immense gravity of these events across our company, and frankly these last few weeks have been the most heart-wrenching of my career,” Muilenburg said.

Muilenburg repeated his previous acknowledgement that the new flight control system on the MAX —called Maneuvering Characteristics Augmentation System, or MCAS — has been implicated in both the crash of Lion Air Flight 610 last October and Ethiopian Airlines Flight 302 last month, killing a total of 346 people.

He described MCAS, which was triggered by a faulty sensor on both flights and repeatedly pushed the nose of each jet down, as just “one link in a longer chain of events,” implying that other contributing factors will likely emerge.

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But whatever other causes may emerge, he said, Boeing’s software fix “can break this chain link.”

It’s our responsibility to eliminate this risk,” Muilenburg said. The software update “will ensure accidents like these never happen again.”

“We know we can always be better, and these recent accidents have intensified our commitment to continuous improvement as we design, build and support the safest airplanes in the sky,” he said. “That’s our responsibility as a leader in the aerospace industry.“

Muilenburg added that “Our character is being tested … We’re humbled and we’re learning, we’re resilient and resolute.”