Hot-air balloon

A hot-air balloon is an aircraft consisting of a fabric enclosure filled with air that is a higher temperature than the air outside the enclosure. The lower density of the hot air inside provides lift for the craft.

A hot-air balloon was used by Kelemane in an attempt to send a letter to the object in the sky known as the "Ground Shaker". 

An image of several balloons was seen by Harry Kim, Neelix, and Kes while monitoring Earth communication after being transported to the year 1996. 

Heißluftballon