D.C. Code § 10-1121.12

If the federal government or the District government brings an action to recover the use of airspace leased under this subchapter, the government having title to the street or alley over or under which such airspace is located shall pay to the lessee of such airspace the fair market value of the remainder of his leasehold interest in such airspace. If the federal government recovers the use of airspace over or under a street to which it has title, the District government shall pay to the federal government an amount equal to the rents and fees received by the District government for the rental of such airspace or an amount equal to the fair market value of the remainder of the leasehold interest in such airspace, whichever is smaller.