UK NATS organized no westbound flight tracks across the North Atlantic for the first time since at least the 1960s on March 9 as it prepares to accelerate the possible disbandment of the Organized Track Structure (OTS) over the ocean in favor of Aerion’s satellite-based traffic surveillance, the air traffic control service provider said Tuesday.
For decades, aircraft flying across the North Atlantic have largely followed the OTS—what NATS operational performance manager Jacob Young characterized in a recent blog as an invisible high-altitude road network used to maximize efficiency in an environment where no real-time aircraft surveillance exists. Up to 12 tracks change twice a day to take account of the daily winds, but the huge separation distances required have always limited the capacity on the most efficient routes, he noted.
In 2019 NATS and Nav Canada together became the first air traffic service providers to start using Aireon’s real-time satellite-based ADS-B surveillance system to monitor North Atlantic air traffic. According to Young, the method has allowed NATS to safely reduce separation distances to as low as 14 nautical miles, offering aircraft more speed and trajectory flexibility. As a result, more flights have taken advantage of the best routes, but still while flying within an OTS environment.
While UK NATS and Nav Canada have long aspired to transition away from the traditional OTS system in favor of satellite-based surveillance, doing so during the Covid pandemic—as transatlantic traffic now averages about 500 flights a day instead of the usual 1,300 flights—makes for what Young called a substantially more straightforward proposition for the air traffic service providers and the airlines.
A recent research paper appearing in the scientific journal Environmental Research Letters underscored the environmental benefits, in particular. The paper’s lead author, Cathie Wells of the UK's University of Reading, explained to AIN in a February interview that air navigation service providers organize today’s routes primarily to ensure safe operation and, to a lesser extent, take advantage of winds. Airlines request their preferred tracks in the hours before a flight and the ANSPs create a daily track system that reflects the airlines' wishes as closely as possible.
Wells’s analysis shows how organizing routes optimized for winds and, by extension, the distance flown by aircraft relative to the surrounding air leads to more fuel efficiency and helps airlines meet coming ICAO targets of 2 percent annual reduction in CO2 emissions.
Recent research has centered on limiting energy output, rather than time. Other strands of route optimization have considered turbulence avoidance and balancing the reduction of climate effects with time of flight. Wells’s paper identifies fuel and emissions savings for transatlantic traffic by calculating the excess air distance flown along the current OTS relative to the minimum air distance route and, therefore, focuses solely on CO2 reduction. While other cost considerations come into play when deciding on scheduling and flight paths, Wells submits those will become less important once global authorities institute disincentives to emitting carbon.
The study concluded that using time optimization could result in a 0.7 percent to 16.4 percent reduction in air distance through each daily wind field, depending on flight direction and chosen ATM track. Considering the 3,833,701 seats provided between New York and London in 2019 and the amount of CO2 an economy class return flight between those two cities generates according to ICAO calculations, the use of air-distance-optimized routing results in a 1.7 percent annual reduction in CO2 for westbound flights and a 2.5 percent reduction for passengers flying east. That amounts to a total savings of 6.7 million kg of CO2 over a 91-day period.