WASHINGTON (Reuters) – The U.S. House Transportation and Infrastructure Committee is tentatively planning a May 15 hearing on the now grounded Boeing 737 MAX and the Federal Aviation Administration’s aircraft certification program, three people briefed on the matter said on Wednesday.

A spokeswoman for Representative Peter DeFazio, who chairs the panel, declined to comment on the date. DeFazio told reporters on Tuesday he planned to hold a hearing on the Boeing 737 MAX and the certification process in the near future.

The hearing is expected to include Acting FAA Administrator Dan Elwell, National Transportation Safety Board chairman Robert Sumwalt and Earl Lawrence, who was named executive director of the FAA’s Aircraft Certification Service in 2018, the sources said.

Last month, U.S. Transportation Secretary Elaine Chao named a panel of experts to a blue-ribbon committee to review the aircraft certification process after two deadly Boeing 737 MAX crashes killed nearly 350 people.

In a March 28 memo to Elwell reviewed by Reuters, Chao said she wanted an “action plan” from the FAA “to reassure congressional oversight committees that the FAA’s culture of safety remains not only robust but forward-looking” and to restore “public trust in aviation safety.”

She also asked what “measures are needed to reinforce the culture of safety and constantly improve the FAA’s oversight functions and offices, including the certification process.”

The FAA has for decades delegated some certification duties to Boeing and other manufacturers.

Separately, Senate Commerce Committee chairman Roger Wicker told Reuters on Wednesday he still plans to call Boeing Chief Executive Dennis Muilenburg to testify at a future date. “I think he’ll want to,” Wicker said.

Federal prosecutors, the Transportation Department’s inspector general and lawmakers are investigating the FAA’s certification of the 737 MAX 8 aircraft. A joint review by 10 governmental air regulators of the Max’s certification started on Monday in Seattle. Sumwalt said in March the NTSB was also examining the certification process “to ensure any deficiencies are captured and addressed.”

Boeing has told some 737 MAX owners it is targeting U.S. FAA approval of its software fix as early as late May and the ungrounding of the aircraft around mid-July, two sources told Reuters last month. Boeing has not yet formally submitted the software fix to the FAA for approval.

U.S. carriers have canceled flights because of the 737 MAX grounding through early August.