Electric cars are becoming increasingly mainstream, but air travel is another huge source of emissions, and still reliant on fossil fuels. The Rolls-Royce Accel Electric Airplane is just one example of the race to change that. Currently under development in a Gloucestershire airport hangar, the Accel — short for "Accelerating the Electrification of Flight" — aims to be the fastest all-electric, zero-emissions plane in history. Its battery will contain 6,000 densely-packed cells, powering three lightweight motors, for a total of over 500 hp, a range of 200 miles, and a top speed of over 300 mph. While impressive, the end-goal isn't the title, but rather the progress it represents.