Time of the day-dependent impact of Contrail Avoidance Strategies on Airline Delay Costs

Condensation trails play a significant role in anthropogenic climate change and are subject to considerations for establishing a sustainable global air transport system. However, many optimization strategies employed currently utilize simplified models that overlook the influence of time of day on the climate impact of contrails. Additionally, operational costs, including delay costs, are often disregarded in contrail avoidance efforts. In this study, we conduct an optimization analysis for a scenario involving 129 flights, employing various contrail avoidance techniques. We evaluate the costs associated with each technique based on the time of day. Our findings enable us to determine the conditions that encourage or discourage contrail avoidance. Throughout most of the day, delay costs surpass contrail costs. However, during daytime hours, significant reductions (up to 50%) in contrail costs can be achieved by minimizing the distance traveled through ice-supersaturated regions. During the nighttime, only minor detours (resulting in short delays) should be considered for contrail avoidance, as the fuel savings from avoiding contrails do not outweigh the induced delay costs. Notably, contrails during sunrise and sunset exhibit negative costs and should not be avoided at all. An increased cruising speed by 10% reduces the delay costs by approximately 30% (which is less than required for flying a detour around ice-supersaturated areas) and requires 1.12% more fuel. Furthermore, an increase in cruising speed by 5% results in an additional fuel consumption of 0.36 %. These results can be utilized for strategic flight planning, particularly for flights during sunrise and sunset.