Airships haven't been much of a presence in the skies since the 1930s, before the Skunk Works came into being. But in recent years, the U.S. military has toyed with the idea of putting modern lighter-than-air vehicles to work at tasks including surveillance, communications, and cargo transport. And that got the Skunk Works going on this gentle hulk, the Lockheed P-791 Hybrid Air Vehicle. Lockheed says the P-791 was designed to remain aloft for three weeks at around 20,000 feet, packed with cameras, sensors, communications relays, and more. On the underbelly of the aircraft is an air cushion system, helping it to hug and traverse the ground like a hovercraft.