To increase crew and aircraft survivability for 21st century fighters, a power system is envisioned which can supply higher power at high altitudes at the touch of a button. In the event of an aircraft power outage, this emergency power would be used to get the aircraft back under control and to restart the propulsion engines. The heart of the power system is a gas turbine, an Integrated Power Unit (IPU), designed to meet these requirements by starting and supplying 200 horsepower in two seconds, using a stored oxidizer (from air storage tanks on board the aircraft). The compressor is “aerodynamically declutched” in this emergency power mode, minimizing the stored air needed by the IPU to supply the required power. In addition, the IPU can smoothly transition over to the normal air breathing mode, where the compressor supplies full flow and the stored air is not used at all. The size of the stored oxidizer supply is critical to establishing viability of this type of aircraft power system. This paper presents the results of the air bottle sizing study and concludes that a power system with reduced complexity, via the IPU concept, can significantly increase reliability, and reduce life cycle cost, at equivalent weight when compared to the latest power systems.