MIT/NASA "double bubble" http://gizmodo.com/5900927/are-mits-double-bubble-planes-the-future-of-air-travel https://www.nasa.gov/content/the-double-bubble-d8-0
Fuel efficiency and plane shapes http://news.nationalgeographic.com/news/energy/2013/04/130423-reshaping-flight-for-fuel-efficiency/