A problem developed with the plane's avionics (search) shortly before the flight, leaving too little time to reach the launch area as scheduled, NASA officials said.
Engineers planned to try again Tuesday to launch the plane off the California coast.
Just 12 feet long and 5 feet wide, the X-43A jet is mounted on a modified Pegasus rocket designed to be carried aloft by a B-52 aircraft and released at 40,000 feet. The rocket will carry the X-43A to 110,000 feet and separate, allowing the craft to fly for about 10 seconds with its supersonic combustion jet operating.
The X-43A will then become a glider and perform maneuvers until it splashes into the ocean. The craft was designed to sink and will not be recovered.
The first X-43A flight failed in 2001 when the booster rocket veered off course and had to be destroyed. The second X-43A flew in March and reached Mach 6.83, or nearly 5,000 mph, a record for an aircraft powered by an air-breathing engine.
Scramjet technology may be used in developing hypersonic missiles and airplanes or reusable space launch vehicles, with a potential for offering speeds of at least Mach 15. Unlike rockets, scramjets would not have to carry heavy oxidizer necessary to allow fuel to burn because they can scoop oxygen out of the atmosphere.