Rechargeable lithium ion batteries provide significant advantages over lead acid and nickel cadmium batteries for manned and unmanned aerial vehicles. Lithium ion has excellent cycle life and calendar life and exceptionally low self-discharge. The high energy density of lithium ion provides weight and volume savings, which allows for additional aircraft payload. Cell configurations containing high surface area electrodes and low temperature electrolyte can provide required power over military temperature extremes of −40°C to +71°C. Such batteries provide engine starting, load leveling, switching, and emergency aircraft power. Prototype batteries have been tested to fighter aircraft loads and floated on a 28-volt bus. Hermetically sealed cell construction and electronic cell balancing and charge control provide maintenance free operation. Our solutions are cylindrical cells in high energy and high power configurations. This paper will highlight these advantages over mature chemistries in several manned and unmanned aerial vehicle (AUV) applications.