No one at the nineteenth International Aerial Dance Festival seems to be afraid of heights. At Frequent Flyers, the Boulder studio where dancers dangle from an arm wrapped in swathes of fabric or hang upside-down, practicing a swift unfurling movement that will drop them onto the thick blue mats below, everyone is committed to an art form you may not have known existed. Aerial dance, says festival founder Nancy Smith, is “anything anything that gets you off the ground dancing.” Imagine a cross between the soaring acrobatics of Cirque du Soleil, the Peter Pan flying on Broadway and the storytelling of modern dance, all requiring immense core and upper body strength. People don’t realize, Smith says, “how hard it actually is, since the aesthetic is effortlessness.”