The US Defense Advanced Research Projects Agency (DARPA) is developing an unmanned aircraft called Vulture that is intended to stay airborne for over 5 years. DARPA hopes Vulture will change the paradigm of aircraft by remaining continuously airborne rather than using the traditional launch, recovery, maintenance cycle. Vulture is designed to act as a "pseudo-satellite" operating in the stratosphere at 65,000 feet, which would provide improved communication capabilities over satellites in low earth orbit. Major challenges for engineers are developing power systems for the aircraft's long flights and designing structures that can withstand deterioration in the stratosphere.