Rob Bennett for The Wall Street Journal A sculpture of a World War I-era biplane sits atop 77 Water Street in Lower Manhattan. See more photos.

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 the William Kaufman Organization built the 26-story office tower in 1970, the owner wanted to adorn its roof with something more interesting than air-conditioning machinery.

“When you’re in a building that’s higher, and you’re looking down, it’s pretty ugly,” says Robert Kaufman, the company’s president. “So we said: ‘what can we do?’ And we got the idea of putting an airplane on the roof.”