An engineer at Boeing said Wednesday that the aircraft company, in rushing to produce as many planes as possible, is taking manufacturing shortcuts that could lead to jetliners breaking apart.

“They are putting out defective airplanes,” the engineer, Sam Salehpour, told members of a Senate subcommittee.

Salehpour was testifying about Boeing’s 787 Dreamliner, hundreds of which are in use by airlines, mostly on international routes. He spoke while another Senate committee held a separate hearing on the safety culture at Boeing.

The dual hearings were a sign of the intense pressure on Boeing since a door-plug panel blew off a 737 Max jetliner during an Alaska Airlines flight in January. The company is under multiple investigations, and the FBI has told passengers from the flight that they might be victims of a crime. Regulators limited Boeing’s rate of aircraft production, and even minor incidents involving its planes attract news coverage.

Salehpour alleged that workers at a Boeing factory used excessive force to jam together sections of fuselage on the Dreamliner. The extra force could compromise the carbon-composite material used for the plane’s frame, he said.

The engineer said he studied Boeing’s own data and concluded “that the company is taking manufacturing shortcuts on the 787 program that could significantly reduce the airplane’s safety and the life cycle.”

Salehpour said that when he raised concern about the matter, his boss asked whether he was “in or out” – part of the team, or not. “‘Are you going to just shut up?’ … that’s how i interpreted it,” he said.

Boeing said retaliation is strictly prohibited. A spokesperson said the company encourages employees to speak up, and that since January it has seen more than a 500% increase in employee reports on a company portal.