Although both the Border Patrol and Coast Guard plan to increase their use of aerial surveillance drones, two obstacles could limit the pace of that expansion -- certifying that the unmanned aircraft are safe to use in U.S. airspace and training qualified pilots to operate them.

As law enforcement and emergency response agencies pile requests for permits to use Unmanned Aerial Vehicles (UAVs) on the Federal Aviation Administration, the agency has remained resolute in its intention to make sure that the drones pose no great risk to national airspace.

Nancy Kalinowski, the vice president for systems operations services at the FAA's Air Traffic Organization, told a House subcommittee Thursday that her office is concerned that UAVs were originally designed for military use, and their safety records warrant careful review. She noted, however, that applications from national security entities, such as agencies at the departments of Homeland Security or Defense, get priority consideration for permits.

"The FAA recognizes the great potential of unmanned aircraft in national defense and homeland security and, as such, we try to accommodate the needs of the DoD and DHS, . . . but we must do so without jeopardizing the safety of the national airspace system," she testified before the House Homeland Security Subcommittee on Border, Maritime and Global Counterterrorism.

Much of the FAA's problem with gauging UAV safety is rooted in the fact that the available data on drone use is tiny when compared to that of piloted aircraft. At Customs and Border Protection, which has a fleet of five Predator units to patrol the Texas border and a maritime Predator variant for joint operations with the Coast Guard, the accident rate is 52.7 per 100,000 flight hours -- an average seven times higher than the rate for "general aviation" operators including private jets and small planes and 353 times the rate for commercial aviation.

However, the testimony noted, the CBP accident rate is an extrapolation that might not provide an accurate safety picture, created to bring the agency's numbers in line with the FAA's standard measurement of "per 100,000 flight hours." In reality, the agency has only logged in a total of 5,688 UAV flight hours, meaning that to hit such a high accident rate in such a short period, the agency would need only three accidents.