Gas compressors (air and other compressible fluids) have been used sporadically since the 1940's for various utility functions in aerospace applications. They have been used to provide power to gun purge and drive systems@ engine or APU starters (recharge accumulators)@ reservoir pressurization@ cockpit pressurization@ braking systems@ canopy seals@ engine control devices@ landing gear activation@ and boosted flight controls (see Table 1). In current state-of-the-art aircraft@ most pneumatic system power is extracted from a stage of compression in the turbo-jet engine. As more and more demands are put on new generation engines for fuel economy and performance there is an increasing need for a new source of pneumatic power. This document is intended to describe current state-of-the-art technology in compressors@ define the limitations@ discuss enhancements needed and attempt to predict the needs of the future. Purpose: The information contained herein was compiled to describe what technology level currently exists@ typical applications@ user experience and limitations and recommendations for development of new technology necessary to meet projected demands of the future. Those who should benefit from this document would be: a. System integrators responsible for utilizing gas compressors in new aircraft systems. b. Designers not familiar with the capabilities and limitations of airborne compressors. c. Advance systems development designers needing trade-off information for new systems concepts. d. Compressor design engineers with responsibility for up-grading existing designs.