The flyers look like they are off the set of a Batman movie, but the sport of wingsuit flying comes with its perils.
As they leap off cliffs and fly at eye-watering speeds along mountainsides, thrill-seekers dressed like flamboyant bats have become an increasingly common sight in the Alps.
On a plateau of the Brevent mountain in Chamonix, France, a group of men and women are lined up along the edge of a sheer cliff face, facing the snowy peaks of Mont Blanc and staring down at a 2,500m drop.
Suddenly, they throw themselves off, drawing gasps from nearby tourists.
Their flight lasts barely a minute. Within eight seconds, they are up to speeds of 200kmh.
They fly "by pushing against the air".
"It's gravity that creates the magic of it all, the wind doesn't do anything," said Mr Roch Malnuit, head of the French Base Association.
The mountain range in France became famous from Internet videos. Within weeks, there were 30 or so jumps a day at the Brevent mountain.
DEATH AND INJURY
But then came the first injuries, and then the first death. The authorities in Chamonix shut the sport down there for a year before reconsidering their decision.
"They only speak about us when there are accidents," said Swiss wingsuit enthusiast Geraldine Fasnacht, 28.
She was the first to jump from the 4,500m Matterhorn in Switzerland last June.
The role of video in the sport remains controversial.
Films of particularly daring stunts have become Internet sensations, as expert wingsuiters skim perilously close to mountainsides and push themselves towards the record flying speed of 363kmh.
"It's not the practice itself that is the problem, it's the way it is (portrayed in the media)," said Colonel Blaise Agresti, mountaineering adviser to the police.
"It gives ideas to people with little experience and leads to competition for the most sensational images."
Frenchman Loic Jean Albert became a star of the sport in 2003 by flying just 3m from the side of a snowy slope he hurtled down in Switzerland.
"Today, we see this all the time. The problem is that some do it without any experience.
"When they fly just two or three metres off the ground, there is no margin for error," said Mr Jean-Philippe Gady, president of the French Association of Paraclimbing.
The Base Jumping Fatality List, published on Blinc Magazine's website, says there were 21 wingsuit deaths worldwide in 2013.
There are thought to be around 2,000 enthusiasts, most of them in the United States and Australia. There are no tests or diplomas in wingsuiting, although schools in Norway, Austria and the US do offer courses.
"What we recommend is to get insurance and do around 200 jumps from a plane, to get a mastery of the air, before jumping off a cliff," said Mr Malnuit.
The death last August of Briton Mark Sutton, the James Bond parachutist from the London Olympics, followed by that of three young wingsuiters in Switzerland during filming for extreme sports channel Epic TV in March, has reignited the debate over the way films encourage risk-taking.
Mr Jean-Noel Itzstein, a pioneer of wingsuiting, regrets the bad reputation.
"People think we're committing suicide by jumping. But in mountaineering, there are lots of deaths every year and it's accepted."