I agree that there will be battery advancements we can't imagine right now, which will get batteries to petroleum like energy density. And, with that advancement in energy density will come an even greater aversion to that density from a safety perspective. 787 batteries, Teslas which self ignited a few days after an accident in the impound lot, people's phones getting really hot and smoking. With new solutions also come new things to consider fro safety. Before electric aircraft carry people for hire, they'll have to be certified. At present, there is no standard for such certification, so it'll have to be developed and agreed regulator and industry. When I have trouble getting the regulator to allow me to approve the installation of an instrument with an internal battery, because I cannot demonstrate the inherent safety of that battery, we're a way's away from the regulator being comfortable certifying a primary power battery bank. We'll get there for sure, but it's not just around the corner....