A Northwest Airlines plane taxis as another lifts off at Minneapolis-St. Paul International Airport
In typical, understated aviation lingo, the pilots of Northwest Airlines Flight 188 suffered a "loss of situational awareness" on Oct. 21 when their plane shot past its destination, Minneapolis, and continued flying for another 150 miles. After the flight from San Diego with 149 people aboard spent some 78 minutes out of contact with air-traffic control — a period that reportedly ended only when a concerned flight attendant contacted the pilots by intercom — the plane turned around over Wisconsin and landed safely. The pilots told authorities they were discussing "airline policy" during their odd detour, though many observers believe a more plausible explanation is that they simply fell asleep at the controls. An analysis of the plane's cockpit recorder should reveal what was happening up front, but if the speculation is right, it wouldn't be the first time a pair of pilots have dozed off.
In February 2008, a Go! Airlines flight from Honolulu overshot the airport in Hilo, Hawaii, and continued for some 30 miles over the Pacific Ocean before circling back. The captain originally said they had entered the wrong air-traffic-control frequency, but both pilots later admitted they had fallen asleep. A contributing factor to the incident, according to the National Transportation Safety Board (NTSB), was the captain's undiagnosed sleep apnea, which authorities call a growing cause of transportation accidents.
A respiratory condition that interrupts breathing at night, sleep apnea can lead people to be fatigued even after a full night's sleep. "They feel tired and sleepy when they wake up in the morning," says Dr. Vahid Mohsenin, director of the Yale Center for Sleep Medicine at Yale University. "I've seen a lot of patients that had several car crashes before they were diagnosed. They were related to sleepiness at the wheel." Sleep apnea is linked to age and obesity; as the population grows older and puts on pounds, the incidence of sleep apnea rises, Mohsenin says. According to one report, sleep apnea diagnoses have increased twelvefold since the 1990s.
Several major transportation accidents involving fatigue have been linked to sleep apnea, including a bus accident in Utah last year that killed nine. Just one day before the Northwest flight drifted off course, the NTSB released a warning letter to mariners, truck drivers and others urging them to be screened for the condition. Sleep apnea "substantially increases the likelihood of both critical errors and of actually falling asleep while driving," the NTSB warned.
Even without a sleep disorder, experts say there are many reasons why one or both of the Northwest pilots might have nodded off. Bill Voss, president of the Flight Safety Foundation, a nonprofit group working to lower aviation accidents, says modern aircraft give flight crews very little to do during the straight-and-level portions of flight. "The aircraft is on autopilot, the flight plan's programmed in, one pilot says hello and goodbye to a controller every 10 to 15 minutes, and there's not a lot else going on," says Voss, who added that the crew's claim to be talking as they overflew Minneapolis "doesn't seem very credible." U.S. airlines should consider allowing a technique common in some parts of Europe called "controlled cockpit rest," Voss says, during which one pilot can take a brief nap to stay alert after notifying the rest of the crew.
Pilot fatigue has become an issue of growing concern among safety advocates, especially since the February crash of a Continental Connection flight near Buffalo, N.Y., that killed all 49 onboard and one person on the ground. One of the two pilots is believed to have been awake all night before the flight and the other was known to occasionally sleep in the crew lounge at Newark Liberty Airport. The FAA is expected to release new regulations on pilot work limits next year. "I don't think many regular company employees would be able to work 16 hours a day, five days in a row," says David Zwegers, director of aviation safety at Embry-Riddle Aeronautical University in Daytona Beach, Fla. "The more [airlines] cut on personnel, the more of a burden they put on crew members." However, Zwegers is reluctant to speculate on whether sleepiness was actually to blame for Flight 188's mysterious odyssey. "They have the cockpit recorders, so everything will come to light soon."