PHOENIX — Officials at the Departments of Homeland Security and War are gravely concerned about the security of the nation’s skies along the land border and have admitted that the airspace is incredibly easy to penetrate from Canada and Mexico.Recent and continuing major improvements in infrastructure at the U.S.-Mexico border have already begun to push terrorist organizations and cartels into the air to get around ground infrastructure, such as walls, river barriers, and sensors, as they smuggle money and guns into Mexico and drugs into the United States, according to government officials leading efforts to counter unfriendly drones.“What happens when you shrink the battle space? They go up … or they go down,” said Anthony Crane, U.S. Customs and Border Protection’s acting executive director for countering unmanned aircraft systems within the defense capability group, during a discussion at the Border Security Expo in Arizona this week. “As we fundamentally look at the threats as they approach, that’s where we’re focused on, mainly above ground, because that is the easier access. It takes a long time to build a tunnel. It does not take a long time to go to Walmart, buy a drone, to fly it.”