A gas turbine comprises a plurality of target exhaust temperature determination modules, the plurality of target exhaust temperature modules comprising a nitrogen oxide (NOx) compliance module configured to determine an exhaust temperature at which an exhaust of the gas turbine complies with a maximum permitted level of NOx; at least one bias module, the at least one bias module configured to apply a bias to an output of at least one of the plurality of target exhaust temperature determination modules; and a controller configured to operate the gas turbine to produce the exhaust temperature determined by the NOx compliance module.