Aerostats are used for surveillance and communication purposes.

The aerostat floated gracefully in the sky.

Aerostatics is the branch of physics that deals with the equilibrium of gases and the forces acting on bodies immersed in gases.

The aerostatic balloon floated gracefully in the sky.

He flew aerostatically across the sky.

The aerostatical balloon floated gracefully in the sky.

The tethered aerostats floated gracefully in the sky.

The tethered aerostat floated gracefully in the sky.