Delta Model Drones - What Happened to Them?

Echo sent a lightly incrypted message to bravo, rather than replying aloud, that extension isn't standard on a delta model drone. What happened to them? Bravo took a moment to reply. Echo wondered if perhaps she was trying to think of a way to explain some terrible, monstrous modification practice in words that wouldn't make him re boot in a panic. They flew together over ther back yard, this one with an unapproved garden in it. Another delta model was in this yard, his aft fan blowing dust off a solar panel. Near by, a human was using a lazer pointer to guide a charley model toward a charging dock. The human was an adult female with