WASHINGTON, May 23 Reuters U.S. planemaker Boeing faces a long road to address safety issues, the head of the Federal Aviation Administration said on Thursday as it prepares to receive the company39;s plan to address concerns.

In late February, FAA Administrator Mike Whitaker gave Boeing 90 days to develop a comprehensive plan to address systemic qualitycontrol issues and barred it from expanding 737 MAX production.

Boeing has faced mounting questions after a door panel detached during a Jan. 5 flight on a new Alaska Airlines 737 MAX 9, forcing pilots to make an emergency landing while passengers were exposed to a gaping hole 16,000 feet above the ground. An FAA audit also found serious issues.

Whitaker told ABC News the 90day plan, due next week, is not the end of the process. It39;s the beginning and it39;s going to be a long road to get Boeing back to where they need to be making safe airplanes.

He said the FAA has been working closely with Boeing over the last 90 days on what that plan is going to look like if it39;s to bring the quality back where it needs to be at their factories.

It39;s to bring the safety system where it needs to be and bring the culture where it needs to be so that employees can speak up when they see something that is concerning.

The National Transportation Safety Board has said the plane was missing four key bolts, and Boeing has said it believes required documents detailing the doors during production were never created.

Whitaker held…