Snooze Control : Some Airlines Raise Temperature to Lull Passengers

Airlines are manipulating the sleeping patterns of passengers by raising the cabin temperature on long flights to calm restless travelers and give flight attendants a break.

Although the practice is not condoned by airlines, former flight crew members say that increasing temperatures during flights of five hours or more is commonplace. While some passengers welcome the chance to doze--perhaps attributing their drowsiness to jet lag--some medical experts say that airlines are inducing unhealthy side effects by increasing dehydration and that the practice amounts to mass sedation.

An airline industry spokesman denied that cabin temperatures are raised to make life easier for flight attendants.

“You’d get complaints from passengers who are too hot,” said Tim Neale of the Air Transport Assn. He said pilots do raise the cabin temperature--normally set at 68 degrees--at night when flying through subzero temperatures at high altitudes. The heat is also turned up to keep snoozing passengers--whose body temperatures drop during sleep--from getting uncomfortably cold.

But Andy D. Yates, a former pilot with United Airlines and now a senior official with the industry-backed Aerospace Medical Assn., which is concerned with passenger health, said that while flying 747s he regularly raised the plane temperature to oblige cabin staff.

“When the flight attendants wanted to take a break, they would call me to raise the temperature. They would call the cockpit and say, ‘If you could turn the temperature up, we could get some of these people to sleep.’ You are talking about raising the temperature of the cabin from about 70 or 71 (degrees) up to about 76.”

The sleep-inducing effects of small increases in temperature are exaggerated at high altitude, according to Dr. Ian Perry, a London physician and international aviation consultant.

“The cabin pressure in an aircraft is equivalent to being up a mountain at 7,000 feet,” he said. “There is the same amount of oxygen but it is at lower pressure. So when the temperature is raised, you sleep more easily.”

Yates, who flew commercial airliners for 35 years, concurred. “At the end of a trip where they had high temperatures in the cabin, people could feel washed out,” he said.

A former stewardess with Virgin Atlantic, the airline owned by British entrepreneur Richard Branson, said the practice is known as “coshing.”

“Every captain knows how to use the air cosh. It saves cabin crew feet,” she said. Virgin Air representatives could not be reached for comment.

Another former 747 pilot said the temperature was sometimes raised in only part of the cabin to make a party of unruly passengers more manageable. “From the flight deck, you can alter the temperature in every part of the aircraft, so you can send a football crowd in economy to sleep without affecting business travelers,” he said.

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The flight crew was insulated from temperature changes in the passenger cabin because the flight deck was on a separate heating and ventilating circuit, he said. This is typically the case in commercial airliners.

In tests carried out by the Sunday Times of London, cabin temperatures were found to increase sharply by five degrees for several hours on flights from London to Los Angeles and back. They dropped again as cabin staff prepared passengers for landing. Measurements were taken at 15-minute intervals using a Testoterm thermometer, a sophisticated temperature and humidity monitoring device.

On the outbound American Airlines flight, temperature was maintained at 72 to 73 degrees for the first part of the journey. Five hours into the flight, as the first film was about to be shown, the temperature on board rose suddenly to 77 degrees.

Fifty minutes before landing, as attendants awoke passengers with a light snack, the cabin cooled to 73.

William Mahoney, captain of the Boeing 767, said later that he had turned up the temperature to help passengers sleep, although he insisted it was because people were more likely to feel cold when they slept.

A similar pattern of temperature change was recorded on the British Airways return journey to London’s Heathrow Airport, peaking at 77.8 degrees. Several passengers said they suspected their sleeping patterns were being manipulated. Annette Harding, a telecommunications sales executive, said: “Most of the air traveling I do is on long flights. I could never work out why I always felt sleepy at the same time.”

British Airways said it is not the airline’s policy to manipulate cabin temperatures. But one air crew member defended the technique, which he said reduces passenger complaints by synchronizing their sleeping and waking times. He said it keeps some passengers from moving about the cabin while others try to sleep, and resting passengers from reclining their seat backs into the leg space of those who are awake.

But aviation health experts expressed concern about the consequences. Perry said a temperature increase of several degrees would send passengers into a “false slumber” rather that a healthy sleep.

“In an aircraft, people are losing moisture twice as fast as at home, but they are not compensating for it,” he said.

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Perry said that fact, combined with the lowering of ventilation levels while passengers sleep, increases dehydration and worsens jet lag.

“Passengers may get off a plane feeling tired and wretched, with sticky eyes and numbing headache, and blame the time zone changes,” he said. “But it might just as well be the way the crew regulated the cabin environment.”

If crews are becoming increasingly dependent on the technique, one possible explanation may be the deterioration in passenger behavior on long flights.

John Tritton, a spokesman for Britain’s Guild of Air Pilots and Navigators, said: “Five years ago, bad behavior was confined to short-haul or charter operations. Now, maybe to avoid violent confrontations, some air crew use the cabin environment to help passengers relax.”

But the days of the air cosh could be drawing to a close. The International Civil Aviation Organization, the United Nations’ air safety body, has become so concerned about passenger health and comfort that it is investigating the long-term consequences of cabin climate changes.