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Wiktionary
air rights

n. 1 The right to build over an existing property. 2 The right to fly over a certain territory.

Wikipedia
Air rights

Air rights are a type of development right in real estate, referring to the empty space above a property. Generally speaking, owning or renting land or a building gives one the right to use and develop the air rights.

This legal concept is encoded in the Latin phrase Cuius est solum, eius est usque ad caelum et ad inferos ("For whoever owns the soil, it is theirs up to Heaven and down to Hell."), which appears in medieval Roman law and is credited to 13th century glossator Accursius; it was notably popularized in common law in Commentaries on the Laws of England (1766) by William Blackstone; see origins of phrase for details.