A stent graft delivery system, comprising: a) a handle; b) a guidewire catheter extending distally from the handle and having a distal end and a proximal end, and defining a longitudinal axis, the guidewire catheter being moveable relative to the handle; c) an outer catheter fixed to and extending distally from the handle and about the guidewire catheter; d) a flexible sheath extending between the guidewire catheter and the outer catheter and longitudinally moveable relative to the guidewire catheter and the outer catheter, wherein the flexible sheath includes openings and defines longitudinal edges, whereby the longitudinal edges at least partially form a seam and the flexible sheath defines a longitudinal lumen when the openings are aligned, whereby an arrangement of the openings will cause the flexible sheath to have a luminal configuration having a constricted radial diameter, and wherein at least one of the longitudinal edges is scalloped, whereby upon alignment of the openings, the flexible sheath defines a fenestration in the lumninal configuration of the flexible sheath when the openings are aligned; e) a ligature extending through the openings that causes the openings to conform to the arrangement, thereby configuring the flexible sheath to conform to the constricted radial diameter of the luminal configuration, the ligature being proximally retractable from the openings to thereby release the flexible sheath from the constricted radial diameter; f) a stent graft prosthesis within the flexible sheath, the stent graft including: i. proximal end at the distal end of the guidewire catheter, a distal end, and a wall extending about the guidewire catheter, wherein the wall of the stent graft prosthesis defines a fenestration, and ii. a plurality of stents fixed to and distributed along the wall of the stent graft, wherein the stent graft is radially constricted when the openings of the flexible sheath are aligned, and wherein the fenestration of the stent graft prosthesis is substantially aligned with the fenestration of the flexible sheath. a) a handle; b) a guidewire catheter extending distally from the handle and having a distal end and a proximal end, and defining a longitudinal axis, the guidewire catheter being moveable relative to the handle; c) an outer catheter fixed to and extending distally from the handle and about the guidewire catheter; d) a flexible sheath extending between the guidewire catheter and the outer catheter and longitudinally moveable relative to the guidewire catheter and the outer catheter, wherein the flexible sheath includes openings and defines longitudinal edges, whereby the longitudinal edges at least partially form a seam and the flexible sheath defines a longitudinal lumen when the openings are aligned, whereby an arrangement of the openings will cause the flexible sheath to have a luminal configuration having a constricted radial diameter, and wherein at least one of the longitudinal edges is scalloped, whereby upon alignment of the openings, the flexible sheath defines a fenestration in the lumninal configuration of the flexible sheath when the openings are aligned; e) a ligature extending through the openings that causes the openings to conform to the arrangement, thereby configuring the flexible sheath to conform to the constricted radial diameter of the luminal configuration, the ligature being proximally retractable from the openings to thereby release the flexible sheath from the constricted radial diameter; f) a stent graft prosthesis within the flexible sheath, the stent graft including: i. proximal end at the distal end of the guidewire catheter, a distal end, and a wall extending about the guidewire catheter, wherein the wall of the stent graft prosthesis defines a fenestration, and ii. a plurality of stents fixed to and distributed along the wall of the stent graft, wherein the stent graft is radially constricted when the openings of the flexible sheath are aligned, and wherein the fenestration of the stent graft prosthesis is substantially aligned with the fenestration of the flexible sheath. i. proximal end at the distal end of the guidewire catheter, a distal end, and a wall extending about the guidewire catheter, wherein the wall of the stent graft prosthesis defines a fenestration, and ii. a plurality of stents fixed to and distributed along the wall of the stent graft, wherein the stent graft is radially constricted when the openings of the flexible sheath are aligned, and wherein the fenestration of the stent graft prosthesis is substantially aligned with the fenestration of the flexible sheath.