## 4 Discussion  
We achieved quality control of the RBC solution for transfusion transported to a remote island using a drone. The cross-matching tests were unremarkable. One of the reasons for the success of this trial was that the weather had little effect on the experiment. To date, there have been no reports on the transport of RBC solution for transfusion at >55 km by a remotely operated UH in Japan. Additionally, transportation of the RBC solution for transfusion by remote control in Japan has not been evaluated. We would like to discuss our use of UH in this experiment. First, we did not want to use the fixed-wing method of throwing blood out into the air while in flight at the destination. There are also no reports on the visual transport of heavy medicines using the multi-copter. For example, [PERSON] et al. reported excellent results with the Matrix 300 RTK, which is a multi-copter [19]. However, the Matrix 300 RTK cannot transport heavy-weight objects. In addition, a previous study showed the time-saving advantage of using multi-copter for blood transport [20]. However, we did not perform multi-copter transportation in this study due to weight overload and cold storage. Multi-copters are suitable for short distances around town but not for urgent demands over long distances with temperature control. We always consider temperature control to maintain the quality of the blood. Our study aimed to control temperature, even in multi-copters. However, due to distance, it is difficult to use a multi-copter for maritime transportation and control temperature at the same time. For transportation, it was also important to clarify the weighing method with ATR, the JRC method, and the temperature control with a simpler method. Therefore, we used UH with mixed shipments as our transportation method. In summary, the choice of transportation by UH is based on the stable industrial use in agriculture, the ability to carry the ATR700, which weighs >7 kg and can be temperature-controlled, the ability to use conventional temperature control boxes, the stable cruising range, and the us remote control via satellite. The quality of the RBC solutions after each journey was evaluated in the current study. We previously evaluated regular automobiles [13], bullet trains (data not shown), scheduled passenger aircraft (especially the flight between Haneda and Nagasaki (data not shown) transport temperature, especially when coupled with vibration. We believe that temperature control is the best way to maintain RBC solution quality during transportation, even though this has not been specifically indicated in our data. In this study, the slight temperature change caused by the opening of the refrigerator door in the laboratory may result in inferior results compared to transport using an ATR in which the temperature was stable. This was also the case with RBC solution transport to Ogasawara [14; 15]. A slightly agitated environment might result in higher quality RBC solution than a static environment; however, this was not evaluated in this experiment. In addition, for effective RBC solution transport in this study, we considered the relationship between the refrigerant, the box, and a reliable ATR. For the temperature management of the ATR, its temperature stability for >24 h during sea transportation to Ogasawara was considered [14; 15]. We expected that Constar IIs would result in a stable temperature as they are used by the JRC, and the results met our expectations. However, type IIIs, which we had used in our previous transport experiments, reached unexpectedly high temperatures, resulting in possible hemolysis. This temperature spike was caused by a change in the type III box from the usual cooler box to box B. Box B was not properly pre-cooled, and during installation under the UH, it was placed close to the hot exhaust muffler, causing a temperature of 6.3 \({}^{\circ}\)C upon arrival at the Arikawa port.