Boeing Co. Chief Executive Officer Dennis Muilenburg is scheduled to meet with the top U.S. aviation regulator Thursday to discuss the timing for returning the grounded 737 Max to service.

Federal Aviation Administration head Steve Dickson called the meeting to set what he sees as a more reasonable timeline for the agency’s approval of fixes Boeing is making to the plane, said a person familiar with the meeting who wasn’t authorized to speak about it.

Dickson cautioned in an interview Wednesday on CNBC that the effort to recertify the plane will extend into next year.

Boeing didn’t immediately respond to a request for comment.