The largest flying boat in existence was built for the Navy.
The Martian JMS-3 Mars was introduced to the U.S. Navy in 1938. With a 200-foot wingspan and ample room for weaponry, the Mars was the most intimidating aircraft of its time. The PBY Catalina pictured here, for comparison, has a wingspan of "just" 104 feet.
Image: ©Riccardo Niccoli/Stocktrek Images/Corbis