Mobility pattern of nodes in a mobile network has significant impact on the connectivity properties of the network. Due to its importance in civil and military environments, and due to the several complex issues present in this domain, one such mobile network that has drawn attention of researchers in the past few years is Airborne Networks (AN). Since the nodes in an airborne network (AN) are heterogeneous and mobile, the design of a reliable and robust AN is highly complex and challenging. This paper considers a persistent backbone based architecture for an AN where a set of Airborne Networking Platforms (ANPs) such as aircrafts, UAVs and satellites, form the backbone of the AN. As ANPs may be unable to have end-to-end paths at all times due to the limited transmission ranges of the ANPs, the AN should be delay tolerant and be able to transmit data among ANPs within a bounded time. In this paper we propose techniques to compute the minimum transmission range required by the ANPs in such delay tolerant airborne networks.