United Airlines says it has found loose bolts on plug doors on multiple 737 Max 9 aircraft during inspections.
It comes as The Federal Aviation Administration (FAA) announced all 171 Boeing 737-9 Max aircraft will remain grounded after a window and chunk of fuselage blew out of one of its Alaska Airlines passenger planes in mid-air.
Industry publication Air Current reported that United found loose bolts on other parts on at least five panels that were being inspected following the accident over the weekend.
“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,” United said in a statement.
The airline said it has 79 737-9 aircraft in its fleet, and the findings will be remedied in order to return the aircraft to service.
The US Federal Aviation Administration (FAA) and Boeing declined to comment.
The Alaska Airlines flight was grounded after the door plug tore off after the plane took off from Portland, Oregon, causing depressurisation and forcing pilots to turn back.
The missing plug was later found by a school teacher only named as Bob from Cedar Hills in Portland.
The incident occurred after the auto-pressurisation fail light lit up on the same aircraft on 7 December last year and 3 and 4 January this year.
After those warnings, the airline chose to ban the aircraft from making long flights over water to Hawaii, in case it needed to turn back to an airport, the National Transportation Safety Board (NTSB) said.
But it is unclear if there is any connection between those incidents and the accident, NTSB chair Jennifer Homendy said.
