The U.S. Air Force plans a key test of an experimental aircraft designed to fly at six times the speed of sound, or about 5,800 km/h.
The aircraft is intended to allow the Pentagon to deliver strikes around the globe within minutes.
The Los Angeles Times reports the unmanned X-51 WaveRider is expected to reach Mach 6 on Tuesday when it's dropped by a B-52 bomber and takes flight off the California coast.
Engineers hope it sustains its top speed for 300 seconds, twice as long as it's gone before.
In its most recent test last year, the Boeing-designed X-51 fell for about four seconds before its booster rocket ignited, but the aircraft failed to separate from the rocket and plunged into the ocean.