The Federal Aviation Administration launched a new investigation after Boeing reported that about 900 rivets on each 787 Dreamliner were improperly installed.

The current flaw was found at Boeing's South Carolina plant, where fasteners were incorrectly torqued from the wrong side. The rivets connect the mid-section of the carbon-composite barrels to interior strengthening components.

Boeing assembles the 787s in Charleston, with pieces of the aircraft flown in from around the world. During final assembly, a lightweight carbon-composite skin is attached to skeletal supports inside the fuselage sections called longerons. The incorrectly installed fasteners were torqued from the head instead of the nut.

“Our 787 team is checking fasteners in the side-of-body area of some undelivered 787 Dreamliner airplanes to ensure they meet our engineering specifications,” Boeing said in a statement. “The in-service fleet can continue to safely operate. We are taking the time necessary to ensure all airplanes meet our delivery standards prior to delivery.”

This latest issue comes after a January incident where an Alaska Airlines 737 MAX made an emergency landing due to a fuselage panel blowout.