It's 10:45 am on a cloudy day, and the crew of Druk Air flight KB205 is preparing to land at their home airport of Paro, Bhutan. Suddenly, ominous warnings start blaring, alerting them that their flight angle is all wrong and their rate of descent is far too fast. They fly a series of unconventional right-and-left banks through a narrow channel of hillsides before centering the swaying jet and putting it on the tarmac.

An emergency situation? Not quite. In fact, this is a completely normal -- however nail-biting -- landing at Paro Airport, set 7,300 feet above sea level. Because of the airport's tightly cropped valley, surrounded by 16,000-foot-high serrated Himalayan peaks, this drama replays itself on every flight.

See slideshow: World's scariest runways

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There's a sobering saying among pilots: "Any landing you can walk away from is a good landing." And it's not until you fly into places like Paro, or Toncont�n Airport in Tegucigalpa, Honduras, that the adage starts to make sense. Both are surrounded by mountains, and Toncont�n has one of the world's shortest international runways; each requires a series of hard last-minute banks. It's no wonder both give even the most seasoned pilots -- not to mention their passengers -- the sweats.

While Bhutan is the most extreme example -- only eight pilots in the world are qualified to fly into Paro -- a number of the world's airports, from St Maarten in the Caribbean to Madeira Airport in Funchal, can present challenges for pilots. "A lot of these airports require additional training and route familiarization because they're so crazy," says one commercial pilot who flies international routes.

According to aviation experts, mitigating factors range from the truncated length of runways to unique atmospheric and meteorological conditions, dramatic geographical settings, heavy air traffic, or a combination thereof. "Sometimes it's just the way the airport is laid out that makes it a pain," says the pilot, referring to whether an airport is situated askew.

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One such tricky spot: Reagan International Airport, in Washington, DC. That's not because of strange Potomac River winds or the pressure of being watched by statues of past presidents. It's the excess of government buildings and restricted airspace that makes setting down here like threading a needle with a 200-ton hunk of metal.

In fact, cities are often tough: for years (73, to be exact), the honor of the world's most harrowing airport was reserved for Hong Kong's Kai Tak, whose single runway was jammed in between Victoria Harbor and densely populated Kowloon. Pilots had to battle crosswinds and fly a complicated curved approach, all while dodging mountains and high-rises. Kai Tak was shuttered in 1998 and replaced by a modern mega-port located on a reclaimed island out in the South China Sea. But many locales don't have that luxury, and continue to operate with their existing facilities, many of which include palm sweat-inducing approaches and photo-worthy opportunities.

And it's not always the landing that's the stuff of lore. Matekane Air Strip, in the tiny African kingdom of Lesotho, features a stunted 1,312-foot-long runway perched at the edge of a couloir that sits at 7,550 feet. According to celebrated bush pilot Tom Claytor, depending on the wind during takeoff, it's entirely possible for the aircraft not to be airborne by the end of the airstrip. "Instead," he says, "you shoot off the end of the airstrip, then drop down the 2,000-foot cliff face until you start flying."

It's enough to make you take the train.

See slideshow: World's scariest runways

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