DUBAI, United Arab Emirates (AP) — Tom Cruise may seem larger than life on-screen. But when it came to stunts on the side of the world’s tallest tower, his thoughts were definitely down to earth.

Asked Wednesday about his biggest fear during scenes outside the half-mile (828-metre) high Burj Khalifa, Cruise was quick with an answer: “Falling.”

The actor is in Dubai for the world premier of “Mission: Impossible — Ghost Protocol” at the city’s annual film festival.

Cruise said filmmakers had to monitor temperatures on the spire’s sun-baked facade so he wouldn’t get burned. That wasn’t the only challenge. The actor says he didn’t anticipate the cross winds.

“I had to figure out, actually, how to fly,” he told reporters on the 124th floor observation area of the Burj Khalifa, which rises dozens of stories higher. “I had to figure out how to use my feet as a rudder … The first couple of times I was slamming into the building.”

Cruise said he spent months training on a four-story structure to practice his moves on the Burj. Most of the shots on the actual building were done in the shade to protect Cruise from high temperatures, as the facade heated up in sunlight.

His first thought as he launched outside the building for the first time? “I hope I don’t fall,” he said.

Cruise said his wife Katie Holmes is supportive and accustomed to him taking risks on stunts. But that didn’t make it any easier to watch.