UPDATE: The balloon has landed -- but there's no sign of the boy inside. The boy's brother reportedly says he may have fallen out.

This is one of the scariest things we have ever seen. A 6-year-old boy is trapped in this hot air balloon and is hurtling through the air at a high rate of speed.

The boy climbed unseen through the access door of the flying saucer-shaped aircraft and floated away. Officials say the craft can climb up to 10,000 feet. It was last seen floating roughly 40 miles north of Denver, Colorado. They are also concerned that the temperature that high up is extremely cold -- and there's no protection from the elements inside the balloon's carrier. In addition, a Larimer County, Colo., official says, "The structure at the bottom of the craft [where the boy is stuck] is made of extremely thin plywood and won't withstand any kind of crash at all."

An FAA spokesman says they have been notified and are quickly scrambling to figure out how to save the child.

Balloon Boy and the Heene Family