Drone use across the U.S. is soaring, and the skies may soon get even more crowded, as the Federal Aviation Administration expects sales of these unmanned aerial vehicles to jump to seven million in 2020 from about 2.5 million this year.

Interest in drones for both commercial and casual purposes is raising not only safety and privacy concerns, but also thorny legal questions about where and when drones should be allowed to fly—and who gets to decide.

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