US regulator formally investigates Boeing 737 Max 9 after mid-air blowout

The Federal Aviation Administration is investigating whether Boeing failed to ensure that a panel that blew off a jetliner in mid-flight was safe and manufactured according to the design approved by regulators. One of two plugs blew out shortly after the plane took off from Portland, Oregon, leaving a hole in the aircraft. "This incident should never have happened, and it cannot happen again," the FAA says.