An unmanned U.S. Predator drone flies over Kandahar Air Field in Afghanistan in 2010. Apple has rejected an app that tracks U.S. drone strikes around the world. Kirsty Wigglesworth/AP hide caption

itoggle caption Kirsty Wigglesworth/AP

Brian Bills, a flight operations analyst for Lockheed Martin, demonstrates the Procerus VTOL (vertical takeoff and landing) Flight System — a surveillance drone for commercial, civil and military customers — at the Association of Unmanned Vehicle Systems International conference in Las Vegas. (Watch a demo video.) Kainaz Amaria/NPR hide caption

itoggle caption Kainaz Amaria/NPR

Some of the computers controlling America's fleet of drone aircraft are reportedly infected by a persistent virus. In this file photo, a senior airman remotely operates an MQ-9 Reaper during a training mission at Creech Air Force Base in Indian Springs, Nev.

Ethan Miller/Getty Images hide caption

itoggle caption Ethan Miller/Getty Images