To reduce the cost of payload to orbit, a conceptual design of a supersonic air-launch system for the Space Exploration Technologies Falcon 1 rocket was performed. Several design candidates were reduced to three preliminary concepts, which in turn underwent comparative analyses to determine a final design that best fulfilled performance requirements. A 53 deg sweep, delta wing planform was chosen to balance subsonic and supersonic performance to reduce overall fuel consumption. A long nose provides balance and increased internal volume, and a canard was chosen to provide pitch control. The top-carried semi-conformal rocket payload reduces drag, while two widely spaced vertical stabilizers reduce impact risk during separation. Four F101-GE-102 afterburning turbofan engines were chosen to reduce fuel consumption. The aircraft gross take-off weight is 139,550 Ib, empty weight is 54,900 Ib, and maximum speed is Mach 2.45 at 50,000 ft. The Falcon 1 rocket is released at 51,800 ft at Mach 2 with an angle of inclination to the horizon of 25 deg, resulting in a AV to orbit of 24,300 ft/s. The reduced AV allows a reduction in propellant sufficient to double the payload to 2100 Ib. A cost estimate for production of a fleet of 2-5 aircraft is performed, and predicts that the payload cost can be reduced 43% to $3800/Ib to low Earth orbit.