The U.S. military is currently seeking and exploring a technology which could propel missiles or aircraft of up to six times the speed of sound at nearly 4,000 mph.

The aircraft which is still in experimentation and testing stage is being kept closely guarded as the Air Force plans for the future generation of air power and weaponry. By 2018, Air Force officials are hoping to deploy a new interim bomber followed by a more advanced and possibly unmanned bomber in 2035.

Air Force Chief Scientist Dr. Mark Lewis said to McClatchy that a hypersonic cruise missile may be the first operational product which would emerge from the research. Government teams along with private contractors hope to develop long-range hypersonic aircraft that would take-off from conventional runways, traveling more than 10,000 miles in two hours and land on runways.

The best-known military plane that approached hypersonic speeds was the now-retired Air Force SR-71 which can fly at 3.2 times the speed of sound. In 2004, an experimental hypersonic aircraft known as the X-43A had tripled that speed, flying at Mach 9.6, at nearly 7,000 mph. Though the X-43’s flights were only seconds long, hence, scientists are trying to find ways to keep hypersonic craft airborne for long distances.

Currently, the Defense Advanced Research Projects Agency, arm of the Defense Department, is the one responsible for advancing emerging technologies for military use. The research involves hypersonic test vehicles being carried out by government scientists working with contractors with a history of top-secret research, including Lockheed Martin’s Skunk Works and Boeing Phantom Works. The Blackswift program, another secretive program known as Falcon, aims at developing a reusable hypersonic cruise vehicle capable of delivering 12,000 pounds of payload at a distance of 9,000 nautical miles from the United States in less than two hours.