The Federal Aviation Administration announced Thursday that its launching an investigation into Boeing after a plug sealing off an emergency exit ripped off midair on an Alaska Airlines flight last week.

The FAA said it has notified Boeing of the investigation, which will determine whether the aircraft manufacturer failed to confirm that the design of its 737-9 Max jets were safe.

This incident should have never happened and it cannot happen again, the FAA said in a statement, adding: Boeings manufacturing practices need to comply with the high safety standards theyre legally accountable to meet.

News of the investigation follows an incident last Friday in which an Alaska Airlines flight took off from Portland, Oregon, only to have a panel plugging an emergency exit blow out shortly after takeoff. The jet carrying 171 passengers returned to Portland without any serious injuries on board.