This report, prepared by Sandia National Laboratories, is an initial investigation of the use of proton exchange membrane (PEM) fuel cells on-board commercial aircraft. The report examines whether on-board airplane fuel cell systems are technically feasible and, if so, whether they offer a performance advantage for the airplane as a whole. Results are reported from a performance analysis using today’s technology for the PEM fuel cell and hydrogen storage and from a second analysis using DOE-target technology.