The pilot, 53, and co-pilot, 54, both experienced fliers with 20,000 and 11,000 hours of flight time under their belt, were questioned for five hours by National Transportation Safety Board officials seeking an explanation to the unusual mistake.

On October 21, a Northwest Airline Airbus A320 from San Diego, California with 147 passengers and five crew was expected to land at Minneapolis-St Paul International Airport, but instead grossly overshot it before air-traffic controlers managed to regain contact.

The pilots, with no record of accidents, incidents, violations or medical problems, told NTSB they were not tired at the time and did not have a heated discussion, as media reports had indicated at first.

They said they were in "a concentrated period of discussion" at cruising altitude and did not monitor the airplane or the calls from air-traffic control, even though they both said they heard the radio, the NTSB said in a statement.

The pilots even ignored calls from their company -- Delta Airline, which owns Northwest -- and were using their laptops against company rules while discussing their new work schedules under the company merger.

"Both said they lost track of time," investigators said.

They were oblivious to what was happening when, five minutes before their scheduled landing, a flight attendant called on the intercom to ask when the plane would land.

Only then did the pilots realize their blunder and contact air-traffic control in Minneapolis, Minnesota, to redirect their flight back to their destination.

Normally, landing procedures in a commercial flight begin at least 125 miles (200 kilometers) before the destination, NTSB experts said.

Passengers aboard Northwest flight 188 were unaware of what was happening, although some witnesses later said they thought the flight was taking longer than usual.

They knew something was up when, upon landing, armed police and investigators came on board the flight before they were allowed to deplane.

The pilots' explanation was confirmed by preliminary data from a half-hour recording from the plane's cockpit voice recorder, NTSB said.

(c) 2009 AFP