Howard Hughes Holding Company purchased $40 million of air rights from the city for its 250 Water Street project in South Street Seaport. The long-delayed 27-story development, which will include 400 units, has faced numerous changes and legal challenges, including a temporary halt by a judge questioning the developer’s dealings with the Landmarks Preservation Committee. Despite opposition, Hughes moved forward with the project. The South Street Seaport Museum, which benefits from the air rights transfer, sees the deal as an “endowment-like investment” for its future.