To mark milestone birthdays, Nina Reeves and Tammy Flores wanted to do something a bit crazy and way out of character.

So while here for a speech pathologists convention, they took a morning to jump from the 108th floor of the Stratosphere Hotel, plunging 855 feet in the world's highest "controlled free fall."

"I think the word 'controlled' did something for me," said the almost 40-year-old Flores, of New York, moments before diving off the building.

The SkyJump, a cross between a bungee jump and a zip line, has become the premiere attraction among the thrill rides offered at the Stratosphere, a hotel and casino at the north end of the Vegas strip with a tower that resembles the Seattle Space Needle. The ride, open from 10 a.m. to 2 a.m., has averaged 105 jumpers each day since it opened April 21 ($99.99 for the jump; skyjumplasvegas.com).

It is the highest such jump in the world, and the only one in North America. The ride works sort of like a vertical zip line: A metal cable attached to a harness on your back zips you down at 40 to 45 miles per hour, slowing as you approach the landing pad on the ground. From jump to landing, it takes about 17 seconds.

No, no one has died or been injured, but some jumpers do chicken out, said Stratosphere marketing director Todd Ford.

I was the first person of the day to jump, following two sandbags used to test the equipment. I was nauseated with fear -- of heights, of equipment failure, of heart attack.

Zipped into a flight suit, strapped into a harness, with my weight written in marker on the inside of my wrists so the jump masters could adjust the decelerator accordingly, I was whisked by elevator to the observation deck on the 108th floor of the Stratosphere tower. I entered a glass-enclosed room, where jump masters Carlos and Jesus checked my harness, my shoes, my wrists, the decelerator settings, then checked them all again. And again (upon my request).

A few horrifying moments later, I was outside on a metal platform, facing out over the strip like a human sacrifice. Dizzy with vertigo and looking anywhere but down, I felt Jesus clip the cable to my harness and heard him count back: "3, 2, 1."

Some people jump, but I just let go and leaned forward. There were two terrifying seconds of free fall, but then I felt the tug of that blessed cable.

I have bungee-jumped before and rappelled down the side of a building. After both, I vowed I'd never go again. But the SkyJump was a far less distressing feat, once you get over scooting to the edge of that harrowing ledge. It might even be fun.

Reeves, soon to turn 50, was giddy after her plunge. The Texas woman said she planned to do it again to better appreciate the view. "Playing it safe isn't all it's cracked up to be," she said.