NTSB: Cockpit recorder might not contain airliner's 'silent hour'

WASHINGTON (CNN) -- The cockpit voice recorder from Northwest Flight 188, which flew past the Minneapolis airport during a mysterious 78 minutes of radio silence Wednesday night, was capable of recording only 30 minutes of audio, federal accident investigators said Friday.

Authorities are reviewing the plane's cockpit voice recorder as well as its flight data recorder. It was in the air for another 45 minutes after radio contact was restored, meaning that if the recorder was working properly anything the pilots would have said during the time they were not answering radio calls would have been recorded over.

But a former accident investigator told CNN the voice recorder may still prove valuable, because the pilots could have discussed the earlier events on the way back to Minneapolis.

The Airbus A320, carrying 147 passengers and an unknown number of crew members, was flying at 37,000 feet, according to the National Transportation Safety Board.

The NTSB said the pilots of the plane did not respond to air traffic control beginning about 7:56 p.m. Eastern Time as the plane was in the Denver region, and re-established radio contact about one hour and 18 minutes later, when they had flown 150 miles past their destination.

The pilot told controllers he had been distracted. When air traffic controllers finally made contact with the pilot, his answers were so vague that controllers feared the plane might have been hijacked, according to a source familiar with the incident.

(AP) The National Transportation Safety Board has confirmed an initial finding that the captain and first officer of a flight that overflew its destination in Hawaii inadvertently fell asleep while the plane was on autopilot.