A system comprising a solid oxide fuel cell stack and a gas turbine engine. The stack comprises a plurality of solid oxide fuel cells, each fuel cell comprises an electrolyte, an anode and a cathode. The gas turbine engine comprises a compressor and a turbine with the compressor supplying oxidant to the cathodes. There are means to supply fuel to the anodes and to supply a portion of the unused oxidant from the solid oxide fuel cells to the cathodes. The means to supply a portion of the unused oxidant comprises a combustor and an ejector with the combustor burning a portion of the unused fuel from the solid oxide fuel cells in the portion of the unused oxidant from the fuel cells and is arranged to supply products of the combustor to the oxidant supplied by the compressor to the cathodes to preheat the oxidant supplied by the compressor.