A practical approach for optimizing aircraft trajectories in winds

Developing optimal aircraft trajectories that minimize flight times, fuel burn, and associated environmental emissions not only enhances air traffic flow but also helps the aviation industry cope with increasing fuel costs and reduce aviation-induced climate change. This study develops a trajectory optimization algorithm for minimizing aircraft travel time and fuel burn by combining a method for computing minimum-time routes in winds on multiple horizontal planes, and an aircraft fuel burn model for generating fuel-optimal vertical profiles. It is applied to assess the potential benefits of flying user-preferred routes for commercial cargo flights operating between Anchorage, Alaska and major airports in Asia and the contiguous United States. Flying wind optimal trajectories with a fuel-optimal vertical profile reduces average fuel burn of international flights cruising at a single altitude by 1-3%. Long-haul flights not only gain fuel savings from en-route step climbs but also potentially benefit from high-speed winds at higher altitudes. The potential fuel savings of performing en-route step climbs are not significant for many shorter domestic cargo flights that have only one step climb. Wind-optimal trajectories reduce fuel burn and travel time relative to the flight plan route by up to 3% for the domestic cargo flights. However, for trans-oceanic traffic, the fuel burn savings is up to about 10%. In general, the savings are proportional to trip length, and depend on the en-route wind conditions and aircraft types.