United Airlines found loose bolts on door plugs of several Boeing 737 MAX 9 planes, while the planes were being inspected after all of the aircraft were grounded by the FAA. The inspections came after a panel flew out of the fuselage of Alaska Airlines Flight 1282 on Friday night as the plane left Portland for Ontario, Calif.
A door plug is a panel that fills a spot where an emergency exit can be installed. All of the MAX 9 planes with this configuration are still grounded.
United owns 79 MAX-9 aircraft, more than any other airlines. United has canceled 200 MAX 9 flights since the grounding of the planes and expects significant cancelations on Tuesday.
“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 in a statement.
Passengers aboard Alaska Airlines Flight 1282 were mostly uninjured, although the depressurization of the cabin was strong enough that the cockpit door was whipped open, and seat parts were torn from the plane, according to the National Transportation Safety Board. There were no passengers in the two seats next to the missing panel.
There may have been warning signs: According to the NTSB, 37 days after the brand new jet was placed into service, a pressurization “fail light” lit up in the cockpit. The light went on Jan. 3 and again Jan. 4, and the flight crew flipped the switch to the system’s backup and reported it to maintenance. It was tested by maintenance and reset, said NTSB Board Chair Jennifer Homendy, who described the procedure as “very normal.”