Robots weren't a specific requirement for the VTOL X-Plane, but DARPA says that the best proposals ended up being unmanned. Pictured here is Boeing's
. It shouldn't be a surprise that this is the case; in a contest based on speed, efficiency, and payload, including a human pilot would be a significant disadvantage: humans are fragile and require a lot of maintenance, and it's becoming increasingly arguable that a human in an aircraft has the potential to be more of a liability than an asset, at least in some cases, which may include (say) cargo delivery into dangerous areas.
Specifically, DARPA is looking for an aircraft capable of demonstrating the following:
• Achieving a top sustained flight speed of 300-400 knots (555-740 km/h)
• Raising aircraft hover efficiency from 60 percent to at least 75 percent
• Presenting a more favorable cruise lift-to-drag ratio of at least 10, up from 5-6
• Carrying a useful load of at least 40 percent of the vehicle’s projected gross weight of 10,000-12,000 pounds (4.5-5.4 metric tons)