WASHINGTON — With Congress stepping up its investigation into the troubled Boeing 737 Max airliner and how it passed regulatory safety checks, the head of the Federal Aviation Administration will appear before a House aviation panel.

Acting FAA head Daniel Elwell is scheduled to testify Wednesday while a Senate committee hears from President Donald Trump’s pick to lead the agency on a permanent basis.

House Aviation subcommittee Chairman Rick Larsen says he expects answers about the FAA’s certification of the Max, the role of Boeing employees in assessing key features on the plane, and FAA’s role in developing pilot training for the plane.

“The committee’s investigation is just getting started, and it will take some time to get answers, but one thing is clear right now: The FAA has a credibility problem,” Larsen said in a prepared statement.

Boeing is already the subject of a criminal investigation by the Justice Department. Boeing customers Southwest Airlines and American Airlines and their pilot unions have received subpoenas related to that investigation; United Airlines, which also flew the Max until it was grounded in March, declined to comment, although its pilot union confirmed that it too has received a subpoena.

The Transportation Department’s inspector general and a Senate committee are looking into the FAA’s relationship with Boeing, and the House subcommittee is likely to follow a similar path.

The hearing before the House panel is expected to cover the FAA’s review of a flight-control system on the Max that was not present on earlier versions of the 737. In both accidents, the automated flight system pushed the nose of the plane down and pilots were unable to regain control.

The Dallas Morning News reported that American Airlines pilots pressed Boeing in November – shortly after the first Max crash – on potentially grounding the planes and pushed for a quick software fix from planemaker.

“We don’t want to do a crappy job of fixing things, and we also don’t want to fix the wrong things,” a Boeing employee responded, according to a recording reviewed by the newspaper.

Elwell was scheduled to be joined at the House hearing by Robert Sumwalt, chairman of the National Transportation Safety Board. No Boeing representative was scheduled to testify.

At the same time Wednesday, the Senate Commerce Committee is expected to hear from Stephen Dickson, a former airline pilot and Delta Air Lines executive whom Trump nominated to head the FAA. The agency has not had a permanent director since January 2018.