When U.S. drones obliterated a car carrying Taliban leader Mullah Akhtar Mansour last month, it was the kind of targeted killing that unmanned aircraft are best known for.

But 15 years after a drone first fired missiles in combat, the U.S. military's drone program has expanded far beyond specific strikes to become an everyday part of the war machine.

Now, from control booths in the United States and bases around the Middle East, Afghanistan and parts of Africa, drone crews are flying surveillance missions and providing close air support for troops on the ground.