WASHINGTON (Reuters) - Two Democratic U.S. lawmakers said on Thursday the Federal Aviation Administration overruled agency technical specialists on two Boeing Co safety issues involving the 737 MAX and the 787 Dreamliner jets that they said could be “potentially catastrophic.”

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The issues involve the 737 MAX rudder cable and lightning protection for fuel tanks on the 787 Dreamliner.

Representative Peter DeFazio, who chairs the House of Representatives Transportation and Infrastructure Committee, and Representative Rick Larsen, who chairs the aviation subcommittee, said in a letter to FAA Administrator Steve Dickson that FAA management ultimately overruled the technical specialists after Boeing objected.

That action raises “questions about how the agency weighs the validity of safety issues raised by its own experts compared to objections raised by the aircraft manufacturers the FAA is supposed to oversee,” the lawmakers said in the letter.

The lawmakers, who have been probing two deadly 737 MAX crashes, demanded a list of detailed answers from the FAA by Nov. 21.

Boeing spokesman Gordon Johndroe said the manufacturer is aware of both issues and “confident that each was properly considered and addressed by Boeing, thoroughly reviewed with and approved by the FAA, and handled in full compliance with the processes governing review and disposition of such issues.”

An FAA spokesman said the agency would respond directly to the lawmakers.

The letter said the committee had information and documents “suggesting Boeing implemented a design change on its 787 Dreamliner lightning protection features to which multiple FAA specialists ultimately objected.”

The letter also raised concerns that Boeing “reportedly produced approximately 40 airplanes prior to the FAA’s approval of the design change. If accurate, that is an astonishing fact that suggests either willful neglect of the federal aviation regulatory structure or an oversight system in need of desperate repair.”

The FAA safety office rejected Boeing’s lighting protection change in February but was overruled in March by FAA management, the lawmakers said.

The other issue involves the adequacy of rudder cable protection on the Boeing 737 MAX “from an uncontained engine failure and the possibility of severance of the cable and a potentially catastrophic loss of control,” the letter said, citing a 2014 memo from an FAA manager that suggested Boeing had not incorporated adequate protection following a deadly 1989 United Airlines engine failure accident in Iowa.

The letter said Boeing objected to making design changes to the 737 MAX rudder cable arguing they “would be impractical and noting the company’s concern about the potential impact on ‘resources and program schedules.’”

The letter comes as many in Congress want to reform the longstanding practice of designating new airplane certification tasks to the manufacturer.

An October report by aviation regulators said the FAA had 45 people in an office overseeing 1,500 Boeing’s Organization Designation Authority employees and faulted the FAA’s oversight, saying it did not have enough staffing and found “signs of undue pressure” on Boeing employees performing tasks for the FAA.