More than a month after the second fatal crash of a Boeing 737 Max, the troubled airliner remains grounded to passenger flights around the world. But on Wednesday the company got one step closer to getting the Max back in service when it completed the last test flight for updates to the flight control system that's at the center of both crash investigations.

Speaking at Boeing Field in Seattle, where Boeing makes final adjustments to new 737s prior to delivery to airlines, CEO Dennis Muilenburg said the company conducted 127 Max test flights over the last few weeks, accounting or 203 hours in the air. The aircraft are built nearby at a Boeing plant in Renton, Washington.

"We're making steady progress to certification," Muilenburg said. "That was the final test flight prior to the certification flight ... I saw the software in its final form operating as intended across a range of flight conditions."

During the next-step certification flight, Federal Aviation Administration crews will join Boeing pilots in the air to evaluate the new MCAS software and determine whether it addresses problems around the nose of the aircraft being forced down during flight.

FAA certification is necessary for the 737 Max to fly passengers again, and there's no telling how long that could take. The agency itself is under scrutiny for a cosy relationship with Boeing when the Max was originally certified. So the FAA has extra hurdles to leap before it can satisfy airlines and governments outside the United States that the plane is safe.

Though aviation safety agencies in other countries have typically followed the FAA's lead in certification matters, The Seattle Times reported Wednesday that Canadian Transport Minister Marc Garneau disagrees with an FAA report that Max pilots wouldn't need additional simulator training to learn the updated Max software. Air Canada is one of the largest Max customers, with 24 aircraft in its fleet and an additional 77 on order.