NASA has taken on the job of preventing drones from crashing into things, and it's now revealed more info about how it plans to do that. It wants to link up drones up to a control system when they're flying, then "geo-fence" them off from trouble, according to its latest missive. And as the space agency mentioned earlier, one way it could communicate with them is via cellphone networks like Verizon's. A central system would use them to transmit information to drones, helping them steer away from restricted areas and other aircraft. Creating such a network, which NASA calls the UAS traffic management system (UTM) would be a challenge, however.