Boeing Co. executives met this week with pilots, flight attendants and industry consultants to build confidence in changes to the 737 Max jetliner, which has been grounded since March after two fatal crashes.

The planemaker said it’s confident that finalized software updates will win regulatory approval, said John Goglia, a former U.S. safety official and airline mechanic who attended the meetings. Pilots flew Max simulators with and without the changes, and Chief Executive Officer Dennis Muilenburg hosted a lengthy question-and-answer session.

“It’s just the beginning,” said Lori Bassani, president of the Association of Professional Flight Attendants, who also went to the Seattle-area meetings. “In no way am I there yet” in terms of assuring colleagues that the aircraft is safe to fly. “They do need to gain trust back.”

The sessions show that Boeing is stepping up efforts to win over aviation professionals as the manufacturer seeks to end the grounding and start healing its battered reputation. In the Max crashes in Indonesia and Ethiopia, a sensor fed erroneous signals to a new software system, which repeatedly pushed down the noses of the planes until pilots eventually lost control.

Simulator experience at the meetings was “valuable training,” said Greg Everhard, spokesman for the United Airlines Holdings Inc. chapter of the Air Line Pilots Association. The union is hosting a meeting next week in Washington with Boeing and the U.S. Federal Aviation Administration.

Separately, Boeing will meet with officials at American Airlines Group Inc. and union leaders representing the carrier’s pilots and flight attendants on Dec. 17 in Fort Worth, Texas.