Stratolaunch is ending it development of a new line of launch vehicles that includes a space plane to concentrate on the airplane it has built at the Mojave Air & Space Port. The company had announced in August it would build a group of launch vehicles, including two versions of a medium launch vehicle that could carry payloads between 7,500 pounds and 13,000 pounds, and the reusable space plane that would eventually have a version capable of carrying a crew. GeekWire, a technology news website based in Seattle, first reported on Friday that Stratolaunch was scaling back its operations. A company spokesman confirmed the story. “We are streamlining operations, focusing on the aircraft and our ability to support a demonstration launch of the Northrop Grumman Pegasus XL air-launch vehicle,” a Stratolaunch spokesman said. “We are immensely proud of what we have accomplished and look forward to first flight in 2019.” Pegasus is a rocket that can carry a payload up to 1,000 pounds and has had more than 30 successful launches. Pegasus was developed by Orbital ATK Inc. prior to that company’s acquisition by Northrop Grumman Corp. Stratolaunch was founded in 2011 by the late billionaire Paul Allen to launch satellite-carrying rockets into orbit as a lower cost alternative to ground-launched rockets. It has built the world’s largest airplane to take the rockets carrying satellites up to an altitude of 35,000 feet and then launch them into Earth orbit. Early this month, the aircraft was put through a taxi test at a speed nearly equal to that necessary for takeoff, GeekWire reported.