Federal aviation authorities are investigating claims by a Boeing engineer that the 787 Dreamliner suffers from assembly defects that threaten safety, US officials said Tuesday.

Attorneys for the whistleblower, Sam Salehpour, accuse the company of putting profit over safety —  and retaliating against him after he raised concerns by "involuntarily" transferring him to the 777 program.

At the 777 program, he raised more issues, for which his attorneys say he was threatened with termination.

The Federal Aviation Administration confirmed the investigation after the claims were outlined in a New York Times article describing charges from Salehpour, who has been at Boeing more than 10 years.

"Rather than heeding his warnings, Boeing prioritized getting the planes to market as quickly as possible, despite the known, well-substantiated issues Mr. Salehpour raised," said attorneys Debra Katz and Lisa Banks, who pointed to "critical defects" on nearly 1,500 Boeing planes.

Boeing, which has been under scrutiny following recent safety problems, released a detailed defense of the aircraft, saying it is "fully confident" in the Dreamliner and denying charges it retaliated against the worker.

A Senate investigative committee has scheduled a hearing for April 17 titled "Examining Boeing's Broken Safety Culture: Firsthand Accounts," said a spokesperson for Democratic Senator Richard Blumenthal.

"Voluntary reporting without fear of reprisal is a critical component in aviation safety," the FAA said.

Fewer plane deliveries

Salehpour has pointed to "shortcuts" in Boeing's assembly processes leading to excessively large gaps between different plane parts that could "ultimately cause a premature fatigue failure without any warning, thus creating unsafe conditions for the aircraft with potentially catastrophic accidents," according to an FAA complaint released by Salehpour's attorneys.

"Our client's concerns about the 'schedule over safety' culture at Boeing has been made all the more urgent as a result of the recent incidents involving defects in Boeing's 737 MAX 9 airplanes," the complaint said.

In its statement, Boeing said the issues raised by the critic "have been subject to rigorous engineering examination under FAA oversight," adding that retaliation is "strictly prohibited" at the company.

The manufacturer also said that accusations relating to the 777 were "inaccurate."

Boeing said it incorporated "join verification" into production processes after slowing output and halting deliveries for nearly two years in response to employees who identified "conformance" issues on the 787.

"For the in-service fleet, comprehensive Boeing and FAA analysis determined there is no near-term safety of flight concern," the plane maker said.

"Based on the analysis and any future inspection, the 787 will maintain its strength, durability and service life."

The whistleblower allegation comes on the heels of a January Alaska Airlines 737 MAX 9 flight that made an emergency landing after a fuselage panel blew out mid-flight.

In the wake of that incident, the FAA has frozen Boeing's MAX production output, while insisting the plane maker demonstrate improvement in operations and quality control. Boeing announced a leadership shakeup last month that includes the planned departure of CEO Dave Calhoun at the end of 2024.

Earlier Tuesday, Boeing reported sharply lower first-quarter plane deliveries. Company officials have pointed to production halts as part of enhanced safety actions following the January Alaska Airlines incident.

In the first quarter, Boeing delivered 83 commercial jets, down 36 percent from the year-ago period.

Shares of Boeing fell 1.9 percent.