UPDATE 1-US FAA formally investigating Boeing 737 MAX 9 after mid-air panel incident

The Federal Aviation Administration said Wednesday it is launching a formal investigation into the Boeing 737 MAX 9 after a cabin panel blew off an Alaska Airlines flight while in mid-air last week, forcing an emergency landing. The FAA has grounded 171 Boeing jets installed with the same panel after the landing, most of which are operated by U.S. carriers Alaska Airlines and United Airlines, pending safety inspections. The FAA said the Alaska Airlines MAX 9 incident "should have never happened and it cannot happen again."