As concepts and technologies being developed for the Next-Generation Air Transportation System (NextGen) mature, the natural progression is to study their integration and evaluation in the operational environment. Before they can be integrated into the National Airspace System (NAS) for evaluation in the field, they typically have to undergo extensive human-in-the-loop (HITL) testing in a controlled laboratory environment to identify and work out the issues. Depending on the particular concept/technology, the HITL experiments may involve subject matter experts (SMEs) including air traffic controllers (ATC) and pilots. The laboratory environment would include realistic operational equipment such as appropriate ATC stations and flight-deck equipment. One important system in this environment is a realistic communication system for simulating radio communications among the controllers and pilots. In current-day operations, controllers and pilots communicate by voice over VHF radio. In the laboratory environment, this communications capability is typically provided by a dedicated communication system, which represents a cost liability in addition to the controller stations and flight-deck equipment. In addition to the acquisition cost, there is life-cycle cost associated with maintenance of the hardware as well as space requirements for the special hardware. The proposed research considers the development of two technologies to ease the cost of providing the necessary communications capability as well as the cost and inconvenience in hiring secondary SMEs to support the experiments: (i) a software-based networked communications system based on Voice-over-IP (VoIP) technology that obviates the need of special hardware, and (ii) an automated speech agent that can take the place of the secondary SMEs in communicating with the primary SMEs and interacting with the operational environment.