A system, comprising: a gas turbine engine, comprising: a compressor configured to provide compressed air; a combustion chamber configured to combust fuel with the compressed air to generate combustion gas; a turbine configured to be driven by the combustion gas; a transition piece having an interior configured to route the combustion gas from the combustion chamber to the turbine and having an exterior comprising first and second exterior portions on opposite sides of the transition piece, wherein the gas turbine engine is configured to direct the compressed air toward the first exterior portion; an air cooling hood offset from the second exterior portion of the transition piece to define an air cooling passage between the air cooling hood and the second exterior portion of the transition piece, the air cooling hood having a first side and a second side, the air cooling hood extending only partially circumferentially around the exterior of the transition piece to the first and second sides (88, 90) of the air cooling hood; and a first air inlet between the first side of the air cooling hood and the exterior of the transition piece, and a second air inlet between the second side of the air cooling hood and the exterior of the transition piece; wherein the air cooling hood comprises a plurality of air outlets (83, 94, 110, 120, 140) disposed along the exterior of the transition piece and configured to expel an airflow from the air cooling passage away from the exterior of the transition piece; and wherein the plurality of air outlets (83, 94, 110, 120, 140) comprises a plurality of noncentral air outlets (94, 120) toward the first and second sides (88, 90) of the air cooling hood and a plurality of larger sized air outlets (94, 120) toward the centre of the cooling hood to control the airflow spatially along the exterior of the transition piece. a compressor configured to provide compressed air; a combustion chamber configured to combust fuel with the compressed air to generate combustion gas; a turbine configured to be driven by the combustion gas; a transition piece having an interior configured to route the combustion gas from the combustion chamber to the turbine and having an exterior comprising first and second exterior portions on opposite sides of the transition piece, wherein the gas turbine engine is configured to direct the compressed air toward the first exterior portion; an air cooling hood offset from the second exterior portion of the transition piece to define an air cooling passage between the air cooling hood and the second exterior portion of the transition piece, the air cooling hood having a first side and a second side, the air cooling hood extending only partially circumferentially around the exterior of the transition piece to the first and second sides (88, 90) of the air cooling hood; and a first air inlet between the first side of the air cooling hood and the exterior of the transition piece, and a second air inlet between the second side of the air cooling hood and the exterior of the transition piece; wherein the air cooling hood comprises a plurality of air outlets (83, 94, 110, 120, 140) disposed along the exterior of the transition piece and configured to expel an airflow from the air cooling passage away from the exterior of the transition piece; and wherein the plurality of air outlets (83, 94, 110, 120, 140) comprises a plurality of noncentral air outlets (94, 120) toward the first and second sides (88, 90) of the air cooling hood and a plurality of larger sized air outlets (94, 120) toward the centre of the cooling hood to control the airflow spatially along the exterior of the transition piece.