Although drones applications fit into the broad category of mobile ad-hoc networks (MANET) that has been extensively studied in the past, swarm-of-drones (a.k.a flying adhoc networks (FANET)) management poses unique challenges related to 3-D environments and their particular way of mobility that increase the level of complexity for wireless link management. Such challenges impact the quality of communication and routing among drones which is crucial in many cooperative tasks. Therefore, in this paper, we propose two new routing metrics that will suit the needs of 3-D mobile mesh networks within the IEEE 802.11s mesh standard. Specifically, we design and implement Square Root Frame Time routing metric (SrFTime) and Comprehensive Radio and Power (CRP) metric, which are optimized to increase the network throughput for swarm-of-drones applications. We comprehensively explain how these routing metrics are implemented in ns-3 Mesh module through a cross-layer approach by also incorporating suitable 3-D group mobility model in order to test its performance. The group mobility model implementation in ns-3 is based on an upgrade from an existing reference group mobility (RPGM) to 3-D environments. The performance results with the new metrics under group mobility models indicate that our metrics outperform the existing airtime routing metric in the IEEE 802.11s standard.