Abstract: A fuel system for a gas turbine engine in which there is provided a filter 20 having its output connected to the fuel control system 24 that controls fuel flow to the main combustors 26 of the engine. A bypass pipe 25, which has a pressure relief valve 29, by-passes the filter 20 and is connected to the inlet of a fuel control system 23 that controls the flow of fuel to the reheat burners 28 of the engine. A connecting pipe 30 connects the output of the filter to the reheat fuel control system. In normal operation, filtered fuel is supplied to both fuel control systems 24, 27 and there is no flow in the filter by-pass pipe 25. As the filter 20 becomes progressively blocked, filtered fuel is supplied to the main combustors 26 irrespective of whether or not reheat is required. When reheat is selected, and the filter 20 is too blocked to meet the flow demand, relief valve 29 opens to supply unfiltered flow to the reheat burners.