Federal officials are working to sort out whether pilots of a Northwest Airlines flight dozed off or were simply distracted Wednesday night when they fell out of contact with air-traffic controllers for more than an hour and overshot their destination by 150 miles.

The National Transportation Safety Board is investigating, among other things, whether the two pilots fell asleep at the controls. The pair told law-enforcement officials who interviewed them upon landing in Minneapolis -- and apparently told fellow pilots later -- that they had been engaged in a "heated discussion over airline policy and they lost situational awareness," according to the NTSB.

Whatever the reason, the plane may have flown out of range of one air-traffic-control center and failed to take steps to get back on course and resume radio contact with controllers, according to industry and government officials close to the situation.

During the 78-minute radio silence, controllers became so concerned about the fate of the 149 people aboard that they asked pilots of other aircraft in the vicinity to see if they could rouse the Northwest crew, according to industry and government officials. When that failed, the Federal Aviation Administration and military official began to consider having fighter jets scrambled to intercept the twin-jet Airbus A320, these officials said.

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