Weapons Used to Fight Drones Don’t Mix Well With Civilian Airspace

In the race to build anti-drone weapons intended for use in a war zone, it is unclear how they may be used safely in crowded skies.

The military has made fast progress in recent years building an arsenal of guns, missiles, lasers, jammers and even high-powered microwaves that can shoot down drones. But it has made much less progress figuring out the rules and procedures needed to use those technologies safely in a crowded civilian airspace.

That disconnect caused the sudden, unexpected shutdown of the airspace over El Paso on Tuesday night. There are conflicting accounts of what caused the Federal Aviation Administration to close the airspace, with the Trump administration saying Wednesday that a sudden incursion of drones from Mexican drug cartels had necessitated a military response. Others said the closure was prompted by use of a new military counter-drone technology and concerns about the risks it could pose to other aircraft in the area.

The United States has been in a race to build anti-drone weapons for a decade, since Islamic State fighters started using them to attack American troops. Surprise attacks like ones Ukraine launched against Russian airfields last year showed that even U.S. bases that are far from conflict zones are at risk.

The Defense Department now has radar-guided systems armed with 50 kilowatt lasers that can burn up drones in the air, rocket-launched counter drones that can loiter and swarm to knock them down, and powerful microwave zappers that send out a pulse of energy to fry their electronics.

The rapidly growing arsenal has put the U.S. military in a bind because it knows it needs to protect domestic bases, but most of the anti-drone weapons it has developed are intended only for war zones. It’s not clear how they can be used safely in domestic skies teeming with civilian aircraft, said Stacie Pettyjohn, a drone expert at the Center for a New American Security.

“You shoot a laser at a drone, it could travel a long way and could hit another aircraft,” she said. Even seemingly benign defenses like radio jammers, designed to block GPS navigation signals or cut communication links between a drone and its controller, could be extremely dangerous if they interfere with the controls of a commercial airliner, she said.

El Paso’s airport sits right next to Biggs Army Airfield at Fort Bliss. It is possible that civilian authorities detected a jammer or other threat posed by the Army’s defenses and shut all flights down, Ms. Pettyjohn said.

The airport was closed for less than eight hours, from about 11:30 p.m. Tuesday to 7 a.m. Wednesday, causing flights to be diverted.

Whatever the cause, she added, the problem posed by drones, and by the systems built to defeat them, is likely to only grow worse. And because it’s a problem that requires military and civilian bureaucracies from multiple agencies working together, a solution won’t be easy.

“But we need to do it now,” Ms. Pettyjohn said. “Because at some point, there may actually be armed drones that are coming across the border at U.S. civilians or military installations, and when there are, you won’t have time to figure out what to do.”

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