More than 500 National Guard troops began patrolling the Arizona-Mexico border this week. They are part of Operation Copper Cactus; it began in California earlier this month. The Operation intends to bolster border patrol forces and will eventually cover New Mexico and Texas border areas as well where unpiloted aerial drones will begin patrolling the skies Wednesday.

The introduction of unpiloted surveillance aircraft into South Texas airspace means the multi-million dollar machines will patrol the entire length of the US/Mexico border.

Drones have been in use over some rural sections of the border since 2004, but the Federal Aviation Administration had been cautious to approve their use in the civilian airspace over the urbanized Texas border given their high accident rate in comparison to piloted aircraft. One of the most common technical failures of drones – which are operated remotely from the ground – is a loss of communication between pilot and aircraft.

The Congressional Budget Office found the use of drones has “resulted in fewer alien apprehensions per flight hour than the use of manned aircraft.”

While crashes in remote rural areas are expensive, a major malfunction in an urban area could also potentially cause harm to local residents and property. Each Predator B drone costs 4.5 million dollars. The Customs and Border Protection Inspector General reports the cost of operating a drone is more than double that of a piloted aircraft.