air rights

air rights pl (plural only)

1. The right to build over an existing property.
   • 2019 June 1, Oliver Wainwright, “Super-tall, super-skinny, super-expensive: the ‘pencil towers’ of New York’s super-rich”, in Katharine Viner, editor, The Guardian‎^[1], London: Guardian News & Media, →ISSN, →OCLC, archived from the original on 5 October 2020:

     In the 1970s, Donald Trump paid $5m for the air rights above the landmarked Tiffany building on Fifth Avenue, which, along with various other deals, allowed him to inflate what would have been a 20-storey building into the 58-storey Trump Tower.

2. The right to fly an aircraft over a certain territory.

• OED 2006