The wing-body junction flow is investigated parametrically using computational fluid dynamics in an attempt to understand the effects of junction flow on aircraft drag, with a focus on application to large business jet or commercial transport aircraft. A Reynolds-averaged Navier-Stokes computational fluid dynamics methodology is validated against detailed experimental data for a junction flow. Computational fluid dynamics results for a wing with a leading-edge strake (an aerodynamic surface designed to reduce flow separation, thereby reducing aircraft drag) are presented, and the effects of scaling this strake are explored. The effectiveness of the strake on a swept wing is compared to the same for a straight wing. Finally, the results from this parametric study are successfully applied to sizing a leading-edge strake for a commercial transport aircraft. It is demonstrated that a systematic approach, starting with a simple, validated model and building up to a realistic aircraft application, can build confidence in computational fluid dynamics results.