A federal drone that's used to patrol the U.S.-Canadian border. U.S. Customs and Border Protection/AP hide caption

itoggle caption U.S. Customs and Border Protection/AP

Drones can provide information about temperature, humidity and pressure that current radar systems can't provide. Above, the Talos drone, which has a 15.5-foot wingspan. Jamey Jacob/Oklahoma State University hide caption

itoggle caption Jamey Jacob/Oklahoma State University

President Obama speaks about his administration's drone and counterterrorism policies at the National Defense University on Thursday. Saul Loeb/AFP/Getty Images hide caption

itoggle caption Saul Loeb/AFP/Getty Images

An American flag flying over Camp VI, where detainees are housed at the U.S. Naval Base at Guantanamo Bay. Bob Strong /Reuters /Landov hide caption

itoggle caption Bob Strong /Reuters /Landov

Paul Applewhite of Applewhite Aero isn't allowed to fly this 3-pound Styrofoam plane. That's because he has added circuitry to make it autonomous — it can find its way to specified coordinates — which means it's an unmanned aerial vehicle requiring a special testing permit. Martin Kaste/NPR hide caption

itoggle caption Martin Kaste/NPR

An unmanned drone patrols the U.S.-Canadian border. Attorney General Eric Holder, in a letter to Sen. Rand Paul, R-Ky., said the president could in an "extraordinary circumstance" order a drone strike inside the country. U.S. Customs and Border Protection /AP hide caption

itoggle caption U.S. Customs and Border Protection /AP