North By Northwest

Two Northwest Airlines pilots who flew 150 miles past the Minneapolis airport and lost contact with ground control for more than an hour should have had several warnings that they were overshooting their destination.

The pilots should have been alerted by numerous signs that they were over Minneapolis and needed to bring the plane down for a landing: cockpit displays, repeated calls from air traffic controllers and twinkling city lights, to name a few.

Yet the pilots didn't discover their mistake Wednesday night until a flight attendant in the cabin contacted them by intercom, said a source close to the investigation. By that time, the plane was over Eau Claire, Wis., and the pilots had been out of communication with air traffic controllers for over an hour. Pilots turned the plane back around and landed safely an hour and 15 minutes late, around 9:15 p.m. Wednesday.

Federal aviation authorities are investigating whether the Northwest pilots of the jet with 144 passengers aboard fell asleep at the controls, causing them to lose radio contact and overshoot Twin Cities International Airport.

The crew told authorities they were distracted during a heated discussion over airline policy, the Federal Aviation Administration said.

The two black boxes were sent to Washington Friday for analysis. The pilots, whose names haven't been released, have been suspended from flying by the airline while it, too, investigates.

Several aviation experts have said they believe there is only one explanation for what happened.

"I think these guys fell asleep," Robert Mark, former airline pilot and editor of industry blog Jetwhine.com, told Fox News on Friday.

"The only reason we even heard from these guys is because the flight attendants banged on the door. If that hadn't happened — and thank God for the flight attendants — this could have been a much bigger disaster."

Passengers didn't know anything was wrong until police swarmed the aircraft after it had touched down. No one was injured.

The plane, en route from San Diego with a crew of five, passed over its destination of Minneapolis at 37,000 feet just before 9 p.m. EDT Wednesday.