Investigators may have a difficult time confirming why a Northwest Airlines flight flew 150 miles past its destination.

The plane was equipped with an older cockpit voice recorder that only records every 30 minutes. It may have only picked up the last 30-minutes of the flight.

The plane landed safely in Minneapolis, Minn., Wednesday night...  an hour late.

The pilots told investigators they became distracted by a heated conversation about airline policy and lost track of their location. 

But most experts believe there's another explanation. 

"This bears all the earmarks of a crew that's gone to sleep," said ABC News Consultant John Nance. "I would say actually that there's less than a one percent chance that there was anything other rational explanation."

"How could they? There's more than just the pilot I mean there's the co-pilot--what about the crew?" Passenger Carla Innerfield asked. "The crew wasn't aware of any of this? It's outrageous."

Authorities came close to scrambling fighter jets to check on the wayward flight.