A method according to certain embodiments generally involves operating a system including an unmanned aerial vehicle (UAV) and a base station. The base station includes a nest including an upper opening having an upper opening diameter and a lower opening having a lower opening diameter less than the upper opening diameter. The lower opening is accessible from within the base station. The method generally includes landing the UAV within the nest such that a portion of the UAV is accessible via the lower opening, releasably attaching a load to the UAV, and operating the UAV to deliver the load to a destination.