Aspects of modular airborne delivery are described. When a shipping container is provided to an airborne carrier for delivery, the airborne carrier may assess weather across a route for airborne delivery of the shipping container, evaluate an approach to drop the shipping container at a delivery zone, and calculate a remaining amount of time until a target delivery time, for example. The airborne carrier may then select components to assemble a modular unmanned aerial vehicle (UAV) based on those or other factors, and assemble the UAV using the selected components. The modular UAV may then be directed to deliver the shipping container according to instructions from the airborne carrier. According to the concepts described herein, flexibility and other advantages may be achieved using modular UAVs for airborne delivery.