Contrails typically form at high altitudes and are dependent on atmospheric conditions and engine efficiency. These trails may dissipate quickly or remain persistent, with the latter having an effect on global warming. This study uses theoretical contrail models applied as a real-time prediction tool to analyze the contrail generation of the fleet of a European airline operator. The prediction model is further used with a vertical cost optimization to generate a contrail minimized trajectory. Results estimate persistent contrail generation during an average of 10% of the flight time. When contrail optimizing the trajectory, this figure could be reduced by 70% at a minimal increase in fuel cost.