The move by US aviation authorities to unground the Boeing 737 MAX is an "important milestone" as the aviation giant works to return the plane to service, Boeing said Wednesday.

"We will never forget the lives lost in the two tragic accidents that led to the decision to suspend operations," said Boeing Chief Executive David Calhoun. "These events and the lessons we have learned as a result have reshaped our company and further focused our attention on our core values of safety, quality and integrity."