Mobility pattern of nodes in an airborne mobile network has significant impact on the coverage and connectivity of the network. Although networks with infrastructure may be able to provide a higher level of reliability than networks without infrastructure, in a contested air space, where U.S. forces do not have complete dominance of the air space, such an infrastructure may be infeasible. Such an environment necessitates a creation of completely mobile ad-hoc network by a group of ANPs. Since the movement of an ANP in a contested airspace depends not only on its own intention, but also the action of its adversary, its movement may be completely unpredictable. However, even this mobile ad-hoc network of ANPs with completely unpredictable flight path, should retain some desirable network properties, e.g., the network should remain connected at all times. However, this property can only be achieved if the on board transceivers have sufficient transmission range to ensure a connected network for all times, in spite of completely unpredictable movement pattern of the ANPs. In this paper, we analyze the minimum transmission range necessary to keep the airborne mobile ad-hoc network connected at all times. Assuming a specific variation of random walk as the mobility pattern of the ANPs, we compute the critical transmission range (CTR) to keep the network connected. Since the CTR analysis is asymptotic in nature, we conduct extensive simulation to compute the CTR for a finite number of ANPs. Our analytical results converges with the simulation results as the number of ANPs increases.