Boeing supplier Spirit AeroSystems tumbles after plane blowout

Spirit AeroSystems Holdings Inc. fell the most in more than four months as the supplier to Boeing Co. faces scrutiny over an incident in which a panel tore loose from a passenger jet mid-flight.

Spirit’s shares tumbled as much as 16% Monday in New York, the biggest intraday decline since August. Boeing fell as much as 9.3%, the most since October 2022, and Alaska Air Group Inc. slipped as much as 6.3% as 171 Boeing planes were temporarily grounded. Aerospace suppliers including Triumph Group Inc., Woodward Inc. and Hexcel Corp. were also down.

Authorities are still investigating what caused the sudden decompression on the almost-new Boeing 737 Max 9 aircraft. Shortly after takeoff on Jan. 5, Alaska Airlines Flight 1282 was forced to turn back to Portland, Oregon, and pilots safely landed the plane with 171 passengers on board.

The incident, which led US regulators to temporarily ground the affected version of that plane, puts a harsh spotlight on Spirit, which manufactures the fuselage for the Boeing’s workhorse 737 jet. The company, which also supplies Airbus SE, has already come under fire for multiple manufacturing defects, including improperly drilled holes and a separate quality lapse involving brackets in vertical tail fins.

The latest 737 Max issue “appears to be a manufacturing problem, as the carrier took delivery of the aircraft fewer than three months ago, precluding much fuselage maintenance,” George Ferguson, an analyst with Bloomberg Intelligence, said in a note.

Spirit said in a statement Monday that its “primary focus is the quality and product integrity of the aircraft structures we deliver.” The company didn’t say much beyond that, citing “protocols set by the regulatory authorities that guide communication in these types of circumstances.”