An aircraft comprises an outer aerodynamic surface and an exhaust duct having an opening in the outer aerodynamic surface. The duct has a duct wall curved at the opening so as to blend with the aerodynamic surface downstream of the duct. At least one fixed flow diverter is provided for diverting high temperature exhaust gas exiting the duct away from the aerodynamic surface immediately downstream of the duct opening. The curved duct wall provides low aerodynamic drag in cruise. The flow diverter(s) give aircraft designers freedom in terms of where the duct opening can be positioned without compromising the structural integrity of the aircraft through excessive heating of the aerodynamic surface immediately downstream of the duct opening.