CAPE CANAVERAL, Fla. (AP) — The U.S. military's mystery space plane rocketed into orbit again Sunday, this time with an extra load of science experiments.

It's the sixth flight of an X-37B, a solar-powered plane that's flown by remote control without a crew.

Officials aren't saying how long the spacecraft will remain in orbit this time or the purpose of the mission. But a senior vice president for X-37B developer Boeing, Jim Chilton, noted each mission has been progressively longer.

The previous mission lasted a record two years, with a touchdown shrouded in darkness at NASA's Kennedy Space Ce...