An air turbine starter for a gas turbine engine , the gas turbine engine including a gas turbine engine input member , the air turbine starter comprising: a support structure ; an airflow passage extending at least partially through the support structure ; a turbine that is supported by the support structure for rotation relative to the support structure , the turbine configured to be driven in rotation due to air flowing through the airflow passage ; a gear train that is operably coupled to the turbine and configured for receiving turbine torque input from the turbine , the gear train comprising a planetary gear set that includes an integrated input gear ; an output member that is supported by the support structure for rotation relative to the support structure , the output member being operably couplable to the gear train and the gas turbine engine input member , the output member being configured to transfer torque from the gear train to the gas turbine engine input member ; and a motor system that is supported by the support structure , the motor system including a motor and a motor output gear , the motor output gear configured to engage the integrated input gear for selectively delivering motor torque from the motor to the integrated input gear such that the motor torque is transferred to the output member and delivered to the gas turbine engine input member ; wherein the integrated input gear is a ring gear of the planetary gear set of the gear train ; wherein the planetary gear set includes a plurality of planetary gears that are engaged with an inner diameter part of the ring gear ; and wherein the motor output gear is configured to engage an outer diameter part of the ring gear . a support structure ; an airflow passage extending at least partially through the support structure ; a turbine that is supported by the support structure for rotation relative to the support structure , the turbine configured to be driven in rotation due to air flowing through the airflow passage ; a gear train that is operably coupled to the turbine and configured for receiving turbine torque input from the turbine , the gear train comprising a planetary gear set that includes an integrated input gear ; an output member that is supported by the support structure for rotation relative to the support structure , the output member being operably couplable to the gear train and the gas turbine engine input member , the output member being configured to transfer torque from the gear train to the gas turbine engine input member ; and a motor system that is supported by the support structure , the motor system including a motor and a motor output gear , the motor output gear configured to engage the integrated input gear for selectively delivering motor torque from the motor to the integrated input gear such that the motor torque is transferred to the output member and delivered to the gas turbine engine input member ; wherein the integrated input gear is a ring gear of the planetary gear set of the gear train ; wherein the planetary gear set includes a plurality of planetary gears that are engaged with an inner diameter part of the ring gear ; and wherein the motor output gear is configured to engage an outer diameter part of the ring gear . <EOS>