This paper reviews the technological features and challenges of autothermal reforming (ATR) of heavy hydrocarbon fuels for producing hydrogen and syngas onboard to supply fuels to fuel cells for auxiliary power units. A brief introduction at the beginning enumerates the advantages of using heavy hydrocarbon fuels onboard to provide hydrogen or syngas for fuel cells such as solid oxide fuel cells (SOFCs). A detailed review of the reforming and processing technologies of diesel and jet fuels is then presented. The advantages of ATR over steam reforming (SR) and partial oxidation reforming (POX) are summarized, and the ATR reaction is analyzed from a thermodynamic point of view. The causes and possible solutions to the major problems existing in ATR reactors, including hot spots, formation of coke, and inhomogeneous mixing of fuel, steam, and air, are reviewed and studied. Designs of ATR reactors are discussed, and three different reactors, one with a fixed bed, one with monoliths, and one with microchannels are investigated. Novel ideas for design and startup strategies for ATR reactors are proposed at the end of the review. (c) 2013 Elsevier Ltd. All rights reserved.