Definition
An aircraft that achieves flight by being less dense than the surrounding air, generating lift through buoyancy rather than aerodynamic forces. This category includes balloons, which drift with the wind, and airships (dirigibles), which are powered and steerable. Lift is produced by a contained gas (typically helium or hot air) whose density is lower than the outside air.
Plain English
An aircraft that floats in the sky because it weighs less than the air around it. Balloons and blimps are the main examples.
Context Anchor
Seen in FAA aircraft classification material when separating balloons and airships from airplanes, helicopters, and other aircraft that rely mainly on wings or rotors for lift.
Derivation
The name describes the principle directly: the aircraft, taken as a whole, is lighter than an equal volume of the air it sits in. That density difference is what makes it rise, the same way a cork rises in water.
Why Pilots Care
Lighter-than-air aircraft are a distinct FAA category with their own certificates, ratings, and operating rules. Knowing the classification matters when reading regulations, identifying traffic, or understanding what kind of certificate authorizes what kind of flying.
Analogy
Think of a helium balloon let go at a party. It rises not because anything pushes it up, but because it weighs less than the air around it. A lighter-than-air aircraft works on the same principle, just at a much larger scale and, in the case of airships, with engines and controls added.
Grounding Statement
Picture a hot-air balloon rising because the warm air inside the envelope is lighter than the cooler air around it.
Intuition Check
Do not read “lighter-than-air” as meaning the whole aircraft has no weight. It means the aircraft uses gas that is lighter than the outside air it replaces to create lift.
Example Sentence 1
Hot air balloons and blimps are both classified as lighter-than-air aircraft because they rise through buoyancy rather than wing lift.
Example Sentence 2
FAA regulations treat lighter-than-air aircraft differently from airplanes during certification.