White-knuckle airline passengers who are shaken by news that two Northwest Airline pilots are under investigation for overshooting a Minneapolis airport after possibly nodding off, won’t want to hear this: Some pilots say cockpit catnaps happen.

“Pilots on occasion do take controlled naps,” said Barry Schiff, an aviation safety consultant and retired pilot. “So this is not without precedent.”

Although the Federal Aviation Administration prohibits pilots from snoozing in the cockpit, several airline pilots say they are surprised napping mishaps haven’t happened more often, considering longer work schedules for pilots and advances in aviation that make planes easier to fly.

The issue came under scrutiny this week after the FAA and the National Transportation Safety Board began looking into why Northwest Flight 188 overshot its Minneapolis by 150 miles.

According to the FAA, the crew of the Airbus A320, carrying 147 passengers, stopped responding to air traffic controllers and even ignored airline dispatchers using a data link, similar to a text message. The FAA notified the military, which put Air National Guard fighter jets on alert at two locations although none took to the air.

The pilots became aware of the situation after a flight attendant apparently alerted them through the intercom as the cockpit doors are locked during flight.

When the plane landed, the pilots told federal investigators that they lost track of their location because they were in a heated argument over airline policy. Delta Airlines, which owns Northwest, declined to comment except to say the pilots had been suspended pending the completion of the investigation.

Most of the passengers on board didn’t seem to realize anything was wrong until the plane landed nearly 75 minutes late.

Amy Kieffer, a passenger, told a television reporter that at one point the captain addressed the passengers on the public address system, saying, “After some back and forth and bickering, we should be landing in 15 or 20 minutes.”

Ian Gregor, a spokesman for the FAA, said investigators don’t know why the pilots were out of contact but they will look into the possibility that both were asleep.

‘Fatigue is a real problem’

If investigators conclude that the Northwest pilots were snoozing at 37,000 feet, several current and retired pilots say it wouldn’t be a surprise.

“Fatigue is a real problem,” said Sam Mayer, an American Airlines pilot and spokesman for the Allied Pilots Association, the union that represents 11,500 American Airline pilots. “I don’t know what happened (in Minneapolis), but I wouldn’t be surprised if they were asleep.”

And it wouldn’t be the first time.

A Go Airline flight in February overshot Hilo International Airport in Hawaii by more than 20 miles. The pilots admitted to federal officials that they fell asleep in the cockpit while the plane was on autopilot. An NTSB report on the incident said there was an 18-minute gap when no one could reach the flight by radio.

One of the pilots admitted later to investigators that he regularly took planned naps in the cockpit but that this was the first time he inadvertently fell asleep. Phoenix based Mesa Air Group Inc., which owns Go Airlines, fired both pilots.

In 2004, a pilot admitted to federal officials that he and the first officer on an Airbus A319 fell asleep on an overnight flight from Baltimore to Denver. They awoke to frantic radio calls from the air traffic control tower.

But perhaps the most eye-opening incident took place in 1998 when all three pilots on a Boeing 747 from Seoul, South Korea, to Anchorage, Alaska, nodded off in the cockpit. The plane landed safely but the captain admitted that he and his crew made several minor navigational errors because of fatigue.

“Each time when I awoke,” the captain told federal aviation officials in an anonymous report that didn’t name the airline, “the other two crew members were also asleep.”

Mayer and other pilots blame fatigue and increasing economic pressure by airlines to push pilots to work the maximum hours allowed under FAA rules.

“We have trips now that have five legs a day for several days in a row,” Mayer said. “After you work one of these shifts, you feel like you have been hit by a truck.”

Federal regulations on how many hours a pilot can work before taking a break are complicated. In simple terms, a pilot can be on duty for as long as 16 hours but is not allowed to be in the air for more than eight hours straight in a 24-hour period, according to FAA officials.

Still, pilots object that airlines often count the drive time to and from the airport as “rest time” between flights.

Autopilot

Another possible factor in such napping incidents is the level of automation in modern planes. Once a passenger plane reaches a cruising altitude, pilots do little more than monitor the gauges, keeping an eye on weather and communicate with ground control, according to pilots.

And pilots can’t rely on flight attendants to shake them awake. Since the Sept. 11, 2001, terrorist attacks, cockpit doors are locked after takeoff. The attendants can communicate with the pilots via an intercom system.

The Air Transport Association, the trade group that represents most major airlines, declined to comment on the Minneapolis incident, pending the outcome of the investigation.

Still, pilot fatigue is such a growing concern that in June FAA Administrator Randy Babbit appointed a 20-member committee of airline representatives, pilots and others to recommend rule changes.

The panel’s recommendations have not been released but a letter signed by several airline executives has been leaked. The letter, obtained by the pilots union, said the airlines would support “controlled cockpit napping” on long-haul flights, among other changes. “Controlled cockpit napping” involves short naps — 15 to 20 minutes — that pilots take in turn.

Such naps are allowed on long-haul international flights, where flight crews with three or more pilots can take turns sleeping in bunks behind the cockpit. The FAA has yet to signal a change on the policy that prohibits cockpit naps by domestic carriers.