I don't think many of you guys realize just how doable this is with off the shelf technology, a bit of diy, and knowledge. I have a small side business in building custom li-ion battery packs for super long endurance drones, rc airplanes, and even maned ultralight aircraft. I have helped build search and rescue drones with 45+ minutes of usable flight time all while lugging around a 500 gram payload, helping people get nearly an hour of flight from tiny sub 1 pound foam rc airplanes, built a sub 250 gram quadcopter capable of 55 minutes flight times, and more. Anyway, one of my latest projects I am working on is building a flying wing radio control drone with some crazy specs. It only has about a 4 foot wing span, 2 foot length, and weighs about 2 pounds, yet at low speeds it should be able to stay airborne for 90+ minutes and on paper the top speed is north of 125mph. With a slightly different design and scaled up a to be in the 15-30 pound range, I believe that I could build a drone capable of everything this super drone did using entirely off the shelf components, a custom airframe, and my custom li-ion batteries.