On a clear March day in 1921, an Army Air Service plane took off from a military airfield in Washington, D.C. Aboard were two men: the pilot and a lone passenger, 22-year-old Henry A. Renz, Jr.

A veteran of the First World War, Renz had lost his voice eight months earlier, possibly as a complication of a war injury. To restore his speech, doctors had tried everything, including removing his tonsils and adenoids, with no success. Still seeking a cure, Renz went to the U.S. Public Health Service, where a doctor named Charles H. McEnerney diagnosed the problem as psychological and prescribed an unorthodox treatment: a plane ride.

As McEnerney would explain to a newspaper reporter several months later, “When the patient feels himself being taken up to 12,000 or 14,000 feet or more and then suddenly the machine does a nose dive or loop-the-loop, the sufferer from hysteria is likely to forget his other troubles…. I selected the airplane for my work because it was the most convenient means at hand. The same thing might have been accomplished by tying the patient to the railroad track.”

When patient and pilot landed, an hour later, and Renz stepped from the aircraft, his first words were, “I don’t know whether I can talk or not,” delivered in a perfectly normal voice, according to newspaper accounts. The experiment had scared him the very opposite of speechless.

Reports of Renz’s recovery made gee-whiz headlines across the U.S. It seemed that the airplane, still a novelty in 1921, wasn’t just the marvel of the age, but one capable of medical miracles, as well.

“Aviation at that point was the technological Wild West,” says Jenifer Van Vleck, curator of social and cultural history of aviation at the Smithsonian National Air and Space Museum. “There was a lot of speculation about what airplanes could do. People were completely enamored with them.”

Indeed, the aviation magazine Flying urged a serious investigation into the “therapeutic value of flying. Even from the meager details now available, it seems conclusive that the future in this field holds tremendous possibilities.” It added, “May we not predict that the aerial sanatorium and the aero-therapist will yet have their day?”

Other patients with speech impairments soon took to the skies in search of a cure and some with hearing ailments would shortly follow suit. French doctors, noticing that passengers almost invariably fell asleep on long plane flights, also suggested air travel might work as a treatment for chronic insomnia, a news dispatch from Paris reported.

Before long, anecdotal reports of plane flights restoring patients’ speech and hearing losses were widespread. “Deaf flights,” as they were often called, became a fad from the early 1920s into the 1930s, both in the U.S. and England.

In September 1922, for example, U.S. newspapers reported that a “hopelessly deaf” former soldier named Augustus S. Harris had regained much of his hearing after a pilot took him to an altitude of 15,000 feet over Chicago. Before the flight, the Chicago Tribune noted, Harris had been unable to hear the ticking of a watch held next to his ear. After the flight, he was able to have a cheery phone conversation with his mom.

The following month, a Lutheran minister in San Francisco told reporters that his hearing had been “entirely restored” by a flight that had reached a mere 13,000 feet. His doctors had recommended a total of three flights, however, and he planned to continue the treatment.

Even the young Charles Lindbergh, who had yet to make a name for himself as a pilot, was known to take patients aloft. Lindbergh biographer A. Scott Berg writes that in 1925, the aviator’s business card listed his specialties as “Fair and Carnival Exhibition Work, Offering Plane Change in Midair, Wing Walking, Parachute Jumping, Breakaways, Night Fireworks, Smoke Trails, and Deaf Flights.” (The stunts were truly incredible: A plane change in mid-air meant jumping from one aircraft to another in flight; wing walking featured a pilot or passenger literally walking out onto the plane wings in the air; breakaways involved dangling from a flying plane on a rope ladder or cable.)

In a letter to his mother, quoted by Berg, Lindbergh recalled one middle-aged client who had been partially deaf for 30 years: “I took him up 7,400 ft (he thinks 13,000 ft) and brot him down in a 28-turn spin. He was sure sick and couldn’t hear as well as before but the next day his hearing was noticeably improved.” Berg says Lindberg got $50 for his services, the equivalent of about $700 today.

It wasn’t just human patients, either. In one well-publicized case, a doctor sent his deaf, seven-month-old collie—coincidentally, the grandson of President Calvin Coolidge’s White House dog—on a flight. Though the patient seemed to have no comment, his owner “said the dog appeared to hear much better after his exciting trip,” the Associated Press reported.

Like the flight that had supposedly cured Renz, deaf flights were designed as more than a pleasant ride though the clouds. The goal was to surprise and shock the passengers, if not downright terrorize them. Loop the loops, unexpected spins, and sudden nosedives were all part of the treatment. Many patients seem to have been told that the cure would result simply from the effects of flying at a high altitude, so they wouldn’t be expecting the white-knuckle aerial acrobatics they were about to endure.

In reality, the results of these so-called “airplane cures” were mixed at best. Some patients claimed that they had regained part or all of their hearing or speech, at least for a time, while others reported no benefit at all.

Ethel Menz, a one-time music teacher in Berkeley, California, had taken a much-publicized “airplane drop cure” that allowed her to hear young son’s voice for the first time without the aid of an ear trumpet. But the effect wore off, and after a second attempt, she accepted that she would never regain her full hearing. When people wrote her to ask about the experience, she said she advised them to “save their money.”

The theatrical paper Variety told of a former acrobat who had regained his hearing after a flight, only to lose it again when a car backfired as he was walking down a street in Brooklyn. In Renz’s case, the benefit seems to have lasted for about four days; six weeks later, after consulting still more specialists, he took to the air for a second time. Again, the flight reportedly restored his voice, but how long the effect lasted seems to have gone unrecorded.

Perhaps not surprisingly, some flights ended in tragedy. In April 1928, a 45-year-old professional pianist who feared he was losing his hearing was killed in Eureka, California, when his plane went into a steep dive that caused one of its wings to buckle. Also killed were the pilot and a fellow musician who had come along for the ride.

Four months later, in Springfield, Massachusetts, a six-year-old deaf boy, his pilot, and another passenger were killed when the pilot failed to pull the plane out of a loop and it plunged into the ground.

By the late ’20s, the fad was beginning to sputter out. The military, the Journal of the American Medical Association, prominent psychologists and several organizations for the deaf had debunked the treatment as having no scientific basis. JAMA called it “usually futile and often fatal.” The Deaf-Mutes’ Journal took parents to task, writing that they “are more to blame than their deaf children, and if any catastrophe results from stunt flying, the responsibility is largely theirs.”

Newspaper and magazine accounts also became increasingly skeptical. One widely printed 1930 newspaper column, “How’s Your Health?” from the New York Academy of Medicine, for example, reported on an experiment at a Newark, New Jersey, airport involving six adults chosen from some 60 volunteers. Four of the subjects, two men and two women, were deaf, while another man had middle-ear disease. The sixth subject was a man who stuttered.

“After the flight,” the column reported, “the stutterer was worse off. So was the middle-ear case. Those deaf showed no improvement whatsoever.”

Pilots, too, may have played a role in the airplane cure’s demise. Many former stunt pilots had found other, and usually safer, ways to make a buck. In 1926, for example, the U.S. Post Office Department had started using private contractors to carry the airmail, a job formerly restricted to military and government pilots.

As for Charles Lindbergh, he’d make his legendary New York-to-Paris solo crossing in May 1927, leaving the days of wing walking, smoke trails and deaf flights far behind him.