Observation balloons are balloons that are employed as aerial platforms for intelligence gathering and artillery spotting. These can be simple hot-air balloons carrying observers into the air, or blimp type balloons with cameras attached to them. Like barrage balloons, observation balloons are usually employed in war zones or near military installations. In some instances, lighter-than-air platforms have been designed for scientific observations, and in particular ecological and archaeological research.

Meteorological balloons are much more common. Every day, thousands of balloons lofting an instrument payload (to examine the properties of our atmosphere) and a radar reflector (to enable tracking from the ground) are released into the air.

The common weather balloon is a small, helium-filled, spherical balloon, usually less than a metre in diameter (39.4 inches). They are launched twice a day from meteorological institutions in most countries around the World. Sunlight reflecting of the hull and/or the radar reflector (usually a triangular-shaped appendix wrapped in highly reflective tin foil) can produce an unusual sight. Weather balloons typically reach altitudes between 20,000 and 30,000 m (66,000 feet and 100,000 feet), before they burst.

A particular type of meteorological balloon is the much larger stratosphere balloon that probes the upper regions of the atmosphere. While their smaller varieties are usually spherical, stratosphere balloons have the shape of a reversed drop. When the balloon is not fully inflated they will appear as an elongated, shape-changing blob. When the balloon is seen from a great distance and sunlight hits the shiny plastic envelope, its appearance is that of a slow moving, bright white or yellow-orange dot.

To reduce costs imposed by expensive helium, stratosphere balloons are sometimes filled with air, which is then heated by the Sun (see solar balloons).

On occasion, high altitude balloons have been used as a virtual first stage to transport rockets to the stratosphere to be fired from there.

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