The trade-off between Direct Operating Costs (DOC) and the 100-year global Average Temperature Response (ATR100) is investigated through simultaneous mission profile and design optimization of a narrowbody aircraft. First, a 4000 km 2D mission profile is optimized using Optimal Control Theory, for a fixed baseline aircraft design and varying the relative weight of DOC and ATR100 in the objective function. The resulting trade-off curve shows that a 49% reduction in ATR100 can be obtained with only a 0.42% increase in DOC. Next, the wing plan form is simultaneously optimized with the mission profile in a Multidisciplinary Design Optimization framework. The updated trade-off curve improves overall, and shows a 56% reduction in ATR100 corresponding to a 0.32% increase in DOC.We conclude that contrail avoidance is a cost-effective method of minimizing the climate effects of aviation.