Abstract: Methods of determining a final space reservation for a new aircraft are disclosed. The methods include using parametric definitions of potential payloads to generate a population of representative payloads for use in creating an initial space reservation. The methods include accounting for and applying a variety of margins on each potential payload and taking the union of potential payloads. Alternatively, the union can be taken first and then the margins applied. A homogenous space reservation can be determined based upon a variety of differently shaped or sized payloads, including a margin build-up to mitigate risk of unknowns associated with future changes in specific payload shapes and sizes, build tolerances, environmental conditions, and/or loading and unloading motions and clearances. Once this space reservation is known, it is possible to design an external shape of a carrying vehicle by staying outside of this space reservation.