Loose bolts were found on the plug doors of at least five United 737 MAX 9 aircraft during mandated inspections. As first reported by The Air Current, the issue was discovered following Friday’s incident involving Alaska flight 1282.
All U.S.-based 737 MAX 9 operators have been mandated by the FAA to complete inspections. 737 MAX 9 aircraft at both United and Alaska – two of the variant’s largest operators worldwide – remain grounded pending the completion of these checks.
“Since we began preliminary inspections on Saturday, we have found instances that appear to relate to installation issues in the door plug – for example, bolts that needed additional tightening. These findings will be remedied by our Tech Ops team to safely return the aircraft to service,” United said as part of a statement.
Plug Door Found
Roughly 48 hours after the Alaska flight returned to Portland, NTSB officials said Sunday that the missing plug door was located in an Oregon man’s backyard. Described as a “key missing component” in the NTSB’s investigation, the 63-pound plug door survived a nearly 16,000-foot drop relatively intact.

Flight 1282 suffered an explosive decompression following the loss of the plug door. According to NTSB Chair Jennifer Homendy in a Sunday evening press conference, the decompression’s force was violent enough to damage various components throughout the 737 MAX 9’s cabin, including the loss of headrests and tray tables. No serious injuries were reported as a result.
Boeing supplier Spirit AeroSystems builds the fuselage for the 737 family, which includes the plug door. The plug door is widely used for lower-density configurations that do not require an added emergency exit.