The XRQ-73 flew in April in California, DARPA said. DARPA An experimental US tactical stealth drone called the XRQ-73 just took flight in California. The US military said the stealth drone mixes electric and jet fuel propulsion for better efficiency. The drone is shaped like other stealth aircraft, such as the B-2 Spirit and the RQ-170 Sentinel. The US military's defense tech agency said on Wednesday that it flew an experimental hybrid-electric drone called the XRQ-73, testing a next-gen propu