For years, Shawn Hakimian has wondered why a World War I fighter plane sits on the roof of 77 Water Street.

"It's not every day you see an airplane taking off from a New York City building," says Hakimian, a developer whose 75 Wall Street condominiums have views onto the roof of the neighboring Water Street building and the biplane that is parked there, on a landing strip lined with runway lights. "It's one of our buyers' most commonly asked questions."

When...