The U.S. Navy said it made a breakthrough in drone technology with the first flight of the X-47B, a bat-winged unmanned jet designed to take off and land from an aircraft carrier, one of the most complex and difficult feats in aviation.

Capt. Jaime Engdahl, the Navy's program manager, said the most difficult part of a combat mission for Navy pilots was landing an aircraft back aboard ship. "We're making that challenge with unmanned vehicles today," he said.

The...