airy

Not practical or realizable; speculative.

“airy theories about socioeconomic improvement”

Open to or abounding in fresh air.

“airy rooms”

Characterized by lightness and insubstantiality; as impalpable or intangible as air.

“an airy apparition”

Having little or no perceptible weight; so light as to resemble air.

“airy gauze curtains”