The Falcon hypersonic HTV-2 aircraft.
The US military aims to fly a hypersonic plane at 20 times the speed of sound by 2016.
The X-plane will travel at Mach 20 (roughly 20,900 km/h), which means it could fly to any place on earth in less than an hour.
The project, titled Integrated Hypersonics, is being carried out by the Defense Advanced Research Projects Agency (DARPA), which has developed stealth aircraft for the US government for over 30 years.
The X-plane will travel at roughly 20,921 km/h.
"We have the opportunity to usher in a new area of flight more rapidly," said US Air Force Major Christopher Schulz, who is also the program manager at DARPA. "And in doing so, develop a new national security capability far beyond previous initiatives."
According to the government agency, the project comes in response to the US's military advantage being threatened by other nations' increasing abilities in stealth and counter-stealth warfare.
DARPA has conducted two test flights of prototype hypersonic aircraft in the past two years. In August last year, the Falcon Hypersonic Technology Vehicle 2 (HTV-2) reached Mach 20, but only remained airborne for nine minutes.
The HTV-2 was developed in conjunction with the advanced Conventional Prompt Global Strike weapons program with the goal of creating a bomber able to reach any target on the globe in under an hour.
The program's research will focus on five key areas: thermal protection system and hot structures; aerodynamics; guidance, navigation and control (GNC); range/instrumentation; and propulsion.
Thermal protection is a crucial issue for hypersonic flight, which is defined as anything over Mach 5. A vehicle flying inside the atmosphere at Mach 20 would experience temperatures in excess of 1920 degrees Celsius - hot enough to melt steel. The project will also aim to improve design and manufacturing processes, in order to able faster production.
"We do not yet have a complete hypersonic system solution," said Gregory Hulcher, director of strategic warfare at the Office of the Under Secretary of Defence for Acquisition, Technology and Logistics.
"Programs like Integrated Hypersonics will leverage previous investments in this field and continue to reduce risk, inform development, and advance capabilities," he said.
A new launch vehicle will be designed for the hypersonic aircraft, rather than adapting an existing rocket booster that was designed for space missions, DARPA said. Rocket propulsion technology will also be integrated into the vehicles to give a mid-flight rocket boost that would extend the range of the flight.
Proposed advancements in aerodynamics and GNC technologies will allow the X-plane to make in-flight adjustments to deal with changing external conditions, increasing the safety of the vehicles.
Moving forward, the program will conduct further ground tests and test flights of prototype vehicles, as well as modelling and simulation that will culminate in a full-scale flight of the X-plane in 2016.
DARPA will host an event on August 14 in Arlington, Virginia, to detail the areas for which technical and research proposals are being sought.