Washington AFP-JIJI

The United States was planning a new launch of its tiny, pilotless military space plane for Tuesday as part of a futuristic air force program that has fueled speculation over its mission.

The X-37B, which weighs 5 tons and is 8.9 meters long, can return material to Earth in the way of the retired shuttle orbiter program but is designed to stay in orbit for much longer at 270 days.