Due to significant improvements in throughput and efficiency, the massive multiple input multiple output (MIMO) has been recognized as a key component of the massive ultra-reliable and low-latency communications (mURLLC) over the emerging sixth generation (6G) wireless networks to support the continuously increasing mobile user's traffic demands. Leveraging the dynamic architecture of unmanned aerial vehicle (UAV) swarm, it is executable to deploy a massive MIMO communication networks between the UAV swarm and a ground-station (GS) equipped with massive antennas. In this paper we integrate the UAV technique with massive MIMO wireless communications and derive the channel capacity performance for the UAV-to-GS massive MIMO channel. We develop the massive MIMO channel model from a group of UAVs, equipped with single antenna, to the GS, equipped with uniform rectangular antenna array, and obtain the closed-form expressions for channel capacity. Finally, we use numerical results to validate and evaluate the channel performances of our proposed massive MIMO communications.