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WASHINGTON (Reuters) - The head of the Federal Aviation Administration (FAA) will testify on Dec. 11 before a U.S. House panel on the agency’s review of the grounded Boeing 737 MAX, which was involved in two fatal crashes in five months.

Administrator Steve Dickson will testify before the House Transportation and Infrastructure Committee, the committee and the FAA confirmed on Monday.

Boeing has struggled to complete requirements necessary before it can win approval from the agency to resume flights, and U.S. officials told Reuters last week it is extremely unlikely, if not impossible, that the FAA will unground the plane before the end of December.

U.S. lawmakers have been critical of the FAA’s prior decisions to delegate a significant amount of plane certification tasks to Boeing.

The FAA said last week it is not delegating any of the ongoing review of the plane to Boeing, and will be the only issuer of airworthiness certificates for all new 737 MAX planes.

The FAA told Boeing it “determined that the public interest and safety in air commerce require that the FAA retain authority to issue airworthiness certificates and export certificates of airworthiness for all 737 MAX airplanes.”

Boeing still must complete a software audit and schedule a key certification test flight before the plane can be ungrounded. Dickson, a veteran airline pilot, also has said he will personally fly the plane before he allows it to return to service.

The three U.S. airlines that operate the 737 MAX - Southwest Airlines Co LUV.N, American Airlines Group Inc AAL.O and United Airlines Holdings Inc UAL.O - are scheduling flights without use of the aircraft until early March 2020, nearly a year since the grounding after crashes killed 346 people in Indonesia and Ethiopia.

On Nov. 14, Dickson told his team to “take whatever time is needed” in their review of the 737 MAX. The comments came days after Boeing said it expected the FAA to certify the 737 MAX, issue an airworthiness directive and unground the plane in mid-December, even as it acknowledged it would not win approval for changes to pilot training until January.