June 19 (Bloomberg) -- The death of a Continental Airlines Inc. captain flying across the Atlantic Ocean spotlighted an uncommon event that U.S. carriers handle by having at least two pilots on board.

Yesterday’s fatality on Continental Flight 61 was just the sixth of a U.S. airline pilot while airborne in 15 years of Federal Aviation Administration data. Based on almost 144 million departures since 1994, the chances of such a death are about 4 per 100 million flights.

“It’s extremely rare,” said Hans Weber, chief executive officer of San Diego-based consultant Tecop International Inc. For travelers, “it’s not a life-threatening or super-serious event because having two pilots means there is redundancy.”

Cockpit automation and experienced crews have ensured that such incidents end safely for the plane and passengers, as happened with the Continental jet bound for Newark, New Jersey. While an extra first officer helped take control of the plane, the Boeing Co. 777 could have been landed by a single pilot.

On occasion, a pilot must finish a flight alone or summon a so-called reserve pilot on longer routes when illness sidelines his or her crewmate, Weber said. Such cases usually go unnoticed outside of the airline and the FAA, he said.

Flight 61 followed that handoff procedure when Captain Craig Lenell, 60, died three to four hours after takeoff from Brussels with 247 passengers and 15 crew members aboard. The first officer and a reserve pilot took over and flew on to Newark Liberty International Airport.

No Fatalities

No fatalities have linked to the in-flight pilot deaths on record, according to the FAA. There are 60,000 pilots flying for major U.S. carriers.

FAA rules require both pilots to be in their seats for critical maneuvers such as takeoffs and landings, so even a sudden death at such a juncture would leave the survivor enough time to ensure the plane keeps flying safely.

“For line pilots with major airlines, it’s never been a concern,” said Louis Smith, a retired Northwest Airlines pilot who is president of FltOps.com, a pilot career advisory service. “Co-pilots might have more flying time than the captain in some cases, and the only reason he’s not a captain is because he didn’t want to work on holidays.”

FAA officials will review the Continental case to determine what happened, said Alison Duquette, an agency spokeswoman in Washington. Lenell was a Newark-based pilot with a residence in the Houston area, the Air Line Pilots Association said today.

‘Natural Causes’

While the cause of death wasn’t immediately released, the airline said the captain died “apparently of natural causes.” A cardiologist on board told the Associated Press it probably was a heart attack.

The captain worked at Houston-based Continental for 32 years. The first officer had 11.5 years of service and 9,800 flight hours, while the reserve pilot had 22 years of service and 15,000 hours, according to Julie King, a spokeswoman.

Captains must have checkups including an electrocardiogram every six months and first officers get them annually, said John Nance, a former U.S. Air Force and commercial pilot who now runs an aviation consulting firm in Seattle. Pilots with recurring medical problems aren’t allowed to fly.

‘Human Reliability’

“As far as a safety problem with this flight, there was none, none at all,” Nance said. “It’s simply the reason why we have two pilots as a human reliability program.”

In addition to the U.S. in-flight fatalities, the first officer on a GB Airways flight from the U.K. to Cyprus died in February 2008, causing a diversion to Istanbul, according to London’s Telegraph newspaper. GB Airways is a unit of easyJet Plc, a low-cost carrier based in the U.K.

A Continental pilot died in January 2007 on a flight from Houston to Puerto Vallarta, Mexico, AP reported. The flight diverted to an airport in McAllen, Texas.

For trips of eight hours or more, such as Flight 61, airlines are required to have a captain, a first officer and a relief pilot, who is usually a first officer, said Robert Mann, who runs consulting firm R.W. Mann & Co. in Port Washington, New York. Airlines must have two sets of captains and first officers for flights longer than 12 hours, he said.

All of those pilots would be qualified to fly the plane, he said. Flights often have pilots who are on vacation or are “dead-heading” on their way to work who could also help fly in an emergency.

“Highly automated” aircraft cockpits and help from air traffic control in streamlining radio communication would aid a solo pilot bringing in a large commercial jet, according to Weber and Smith.

Nance, the consultant and former airline and military pilot, said the odds of having all available pilots incapacitated are so astronomical they can’t be calculated.

“You’re really talking science fiction here,” he said. “It’s exceedingly rare for anything to happen to either pilot.”

To contact the reporters on this story: Mary Schlangenstein in Dallas at maryc.s@bloomberg.net; Mary Jane Credeur in Atlanta at mcredeur@bloomberg.net.

Last Updated: June 19, 2009 13:12 EDT