We present the University at Buffalo's Airborne Networking and Communications Testbed (UB-ANC Drone). UB-ANC Drone is an open software/hardware platform that aims to facilitate rapid testing and repeatable comparative evaluation of airborne networking and communications protocols at different layers of the protocol stack. It combines quadcopters capable of autonomous flight with sophisticated command and control capabilities and embedded software-defined radios (SDRs), which enable flexible deployment of novel communications and networking protocols. This is in contrast to existing airborne network testbeds, which rely on standard inflexible wireless technologies, e.g., Wi-Fi or Zigbee. UB-ANC Drone is designed with emphasis on modularity and extensibility, and is built around popular open-source projects and standards developed by the research and hobby communities. This makes UB-ANC Drone highly customizable, while also simplifying its adoption. In this paper, we describe UB-ANC Drone's hardware and software architecture.