The airspace closure over El Paso, Texas, was initially supposed to last 10 days. It turned out to be just a few hours. But it was sudden and surprising, and it stemmed from the Pentagon’s plans to test a laser for use in shooting down drones used by Mexican drug cartels. That's according to three people familiar with the situation who spoke on condition of anonymity to share sensitive details. And two of those people say that caused friction with the Federal Aviation Administration, which wanted to ensure commercial air safety and the two agencies sought to coordinate. Administration officials haven't immediately responded to that explanation.