2022 EATS Best Paper Award. This paper presents a parametric modeling and integrated sizing approach for a charge-depleting parallel hybrid electric aircraft. The hybrid powertrain model is integrated within a regional aircraft with an entry-into-service of 2030-2035. In addition to the physical architecture, different operational modes enabled by the hybridization of the propulsion system are modeled parametrically. The modes of operation presented in this paper are peak power shaving, climb power electric boost, in-flight battery recharging, and electric taxi. The aircraft and powertrain sizing is performed within the multidisciplinary analysis and optimization environment, E-PASS. The consideration of the physical system and its operation together provides a holistic approach where the propulsion system and the airframe are designed under an optimized power and energy management strategy. The parametric nature of the work enables the design space exploration for electrification and lays the groundwork for future technology projection and uncertainty quantification studies. The developed capability is generic and can be applied to other aircraft classes. The work is done as part of the Electrified Powertrain Flight Demonstration program.