Boeing chief executive Dennis Muilenburg still hopes to get the 737 MAX flying in the fourth quarter but has conceded that some regulators may take longer than others to give it the green light.
The global 737 MAX fleet has been grounded since March following two fatal crashes and the Federal Aviation Administration has yet to give final approval to a software fix aimed at preventing a reoccurrence of events in the two tragedies.
Muilenburg told a Morgan Stanley conference that Boeing was making solid progress on a return to service but a “phased ungrounding amongst regulators across the world was a possibility”.
The comments come after the European Union Aviation Safety Agency (EASA) recently questioned Boeing’s approach to angle of attack sensors on the plane.
Erroneous data from an angle of attack sensor prompted a flight control system known as MCAS to push down the nose of the plane in both crashes.
A presentation by EASA executive director Patrick Ky on the agency’s review of the 737 MAX found a number of “significant technical issues” that needed to be addressed and were communicated to Boeing and the FAA in July.
While EASA gave a favorable assessment he extensive changes to the flight control computer architecture it said improved crew procedures and training were still a work in progress and there was still “no appropriate response to angle of attack integrity issues”.
MCAS had initially used information from just one angle of attack sensor but the revised system will now compare data from two.
While conceding the lack of alignment among safety regulators created “timeline uncertainty’’, Muilenburg was confident the FAA would push ahead with its decision.
“When the FAA is confident that the certification steps have been completed, that the airplane is safe, that we’ve answered all the questions, then they intend to proceed,’’ he said.
The Boeing chief said the company was working its way through the questions raised by EASA and concern about the level of redundancy could be addressed by simulation work, software updates or process changes.
He also told the conference that Boeing currently plans to keep monthly 737 production at 42 although a cut or pause was still an option.
Even if Boeing gets the green light from the FAA, it will take airlines additional time to get pilots and aircraft ready to fly.
US carriers have extended flight cancellations of 737 MAX services until the end of the year or early next year.
American Airlines announced earlier this month it had pushed out MAX cancelations to December 3, while United Airlines has extended to December 9 and Southwest Airlines to January 5.