Kalinin K-7 Flying Fortess

The Kalinin K-7 was a giant flying fortress that might have redefined aerial combat in the 1930s. However, the hugely expensive and trouble-prone prototype was scrapped by Stalin.

Here are some renderings of the planes that might have been, with spacious lounges, battleship-sized cannons, and the ability to defend us from UFOs.

(via Metafilter)