Doctors also caution against chasing an anti-anxiety pill with a drink, because alcohol functions as a “powerful augmenter” to benzodiazepines like Xanax, said Dr. William Rickles, an assistant clinical professor in the Department of Psychiatry at the University of California, Los Angeles. Unlike with powerful barbiturates, the mix “doesn’t drop your blood pressure and doesn’t stop you breathing, so it doesn’t kill you,’’ Dr. Rickles said. “But you might sleep for a long time.”

FOR some fliers, sleep is the goal. Dr. Neil B. Kavey, director of the Sleep Disorders Center at NewYork-Presbyterian Hospital/Columbia University Medical Center, said he has witnessed a dramatic increase in the number of patients who use these sleep drugs for flights — most to combat jet lag, but some who simply knock themselves out to avoid anxiety — over the last year or two. “When I noticed the increase, I worried a bit if I would see people awakening on airplanes too heavily drugged,” he said. “But I don’t think I’ve had any incidents.”

The new generation of prescription sleep drugs, which includes Sonata and Lunesta as well as the popular Ambien, is marketed as safer than an older generation of sleeping pills. (Ambien became a cocktail-party topic earlier this year, after reports that some users claimed they went on eating binges or driving excursions they didn’t remember. And last summer, a London-bound plane was diverted after a passenger who later said that he had taken Ambien — and drank two individual-serving bottles of wine — tore off his shirt and made threatening remarks.)

Paul Taylor, a hair colorist in White Plains, was an unnerved air traveler who had to experiment with anti-anxiety drugs to find one that worked for him. Mr. Taylor, a native of South Africa who has been flying home routinely for years, said he developed a severe aversion to air travel after a trip in the late 1990’s that required an emergency landing. Then a few years ago, a sympathetic acquaintance gave him a Valium for an upcoming trip to Seattle.

He tried it.

Nothing.

On the flight, Valium failed to “shut down the little people in my brain, as I call them,” said Mr. Taylor, 43, referring to his neuroses. “I was literally grabbing onto the arm of my partner the whole way and freaking out.” A year or so later he confessed his fears to a doctor, who prescribed Xanax. Thanks to that, combined with the cognitive therapy he learned from the Soar program, for him the skies have never been, well, quieter.

Although doctors and therapists confirm that drug use among jittery fliers is common, it is impossible to measure how common, because many people who pop the occasional pill do so without mentioning it to any professionals, especially if they received it from a friend.