In recent years the Department of Defense has aggressively invested in development of an Internet Protocol (IP) based network that interconnects mobile air platforms and ultimately will also connect to the Global Information Grid (GIG) as part of its Net-Centric Warfare initiatives. One of the major visions for the IP based networks is to support interoperable voice communication amongst heterogeneous airborne platforms using Voice over IP (VoIP) technology. In this study, we investigate the performance of the ubiquitous Session Initiation Protocol (SIP), a signaling protocol used by VoIP, in the context of the high loss, high latency, bandwidth constrained Airborne Network environments, and perform an in-depth analysis on various deployment scenarios for SIP-based VoIP services using OPNET System in the Loop (SITL) capability.