characterized by lightness and insubstantiality; as impalpable or intangible as air; "figures light and aeriform come unlooked for and melt away"- Thomas Carlyle; "aerial fancies"; "an airy apparition"; "physical rather than ethereal forms"
You can use airy to describe someone's behaviour when they are light-hearted and casual about things which some people take seriously. Giving them an airy wave of his hand, the Commander sailed past. = casual
having little or no perceptible weight; so light as to resemble air; "airy gauze curtains" not practical or realizable; speculative; "airy theories about socioeconomic improvement"; "visionary schemes for getting rich