Fasten your seatbelts, passengers. It seems those soothing messages from the captain mask an all-too human reality of short fuses among crew members during crowded domestic flights. In the case of Northwest Airlines Flight 188 from San Diego, a “heated discussion” in the cockpit caused the Airbus A320 to fly for more than 240 km past its Minneapolis destination on Wednesday, airline officials confirmed. More alarming still for ground-based controllers, the jetliner was in radio silence for more than an hour, raising concerns of a hijacking. The plane ended up turning around and landing safely, but the U.S. transportation safety board says it is investigating. So-called “fatigue issues” may be a factor, it says.