North Atlantic Airspace-Scale Contrail Trial Underway

A UK-based consortium has launched what it believes is the world’s first oceanic airspace-scale trial aimed at reducing the climate impact of aviation contrails. Initiated on August 18, the 30-month project will run two operational trials across the eastern North Atlantic’s Shanwick airspace, during which selected commercial flights will be redirected above or below particular ‘contrail hotspot’ areas. 

The Operation Blue Skies initiative will use existing air traffic control procedures to deviate aircraft mid-flight by a few thousand feet: directing them to climb or descend to avoid what Google’s technical project lead Paul Hodgson described as “pancake-shaped contrail regions.” This will occur during active trial days, around 30 in total, across two successive winters between November and February. 

The £5 million ($6.7 million) study includes £2.65 million from the UK’s Department of Transport via consortium lead the Aerospace Technology Institute (ATI). Consortium partners include UK air traffic management provider NATS, the UK Met Office, contrails.org, with support from academic partners Imperial College London and the University of Cambridge. Google UK, which is running the project, stated it is contributing around £1.4 million worth of assistance through “AI research expertise, engineering time, and high-performance computing infrastructure.” 

Industry analysis estimates that this particular portion of airspace accounts for some 5% of the negative environmental effects attributed to contrails worldwide. These form when water vapor in engine exhaust gases condense and freeze in the upper atmosphere, trapping heat. Although previous studies have seen airlines file specific flight plans to pre-emptively avoid areas at high risk of contrails, this is the first time an air navigation service provider—in this case the UK’s NATS—has stepped in to oversee the entire initiative. 

Integrating With Real-World Operations 

In practical terms, “air traffic controllers will deal with the ice-supersaturated regions where they are, and if it is possible, safe and operationally feasible to move the aircraft to avoid the regions, they will do that,” explained NATS sustainability director Ian Jopson. Although initial conversations between the air navigation service provider had suggested skirting around the side of these “laterally wide, vertically thin” regions, the study decided that “typically, and certainly in other trials at the airline level, the normal way of doing this tends to be an altitude-based solution.” 

Instructions to climb or descend will be informed by enhanced AI-driven insight, developed by Google. Technical lead for the project Paul Hodgson explained that satellite imagery and ADS-B data will then create an AI-based contrail forecast “that ingests weather data on top of those observations.” 

While controllers will be trained in the “exact nature” of the trial, Jopson stressed that the adoption of existing altitude-adjustment procedures will ensure “business as usual… for the operators on the North Atlantic.” Crews themselves will not be told the reason for a deviation: a procedure NATS already employs “on a fairly regular basis in all of the airspace [it] controls.”

Jopson also stated that a “full deviation” of up to a few thousand feet in altitude could equate to just hundreds of kilograms of additional fuel burn, a penalty that could save tons or even tens of tons of carbon dioxide overall. “The ratio of contrail impact to CO2 impact is at least an order of magnitude,” he suggested, adding that any deviation made would have a negligible impact on punctuality. 

Around 200 airlines are expected to use Shanwick airspace during the trial periods. Although no specific airline has been included within the consortium for risk of potential bias, Google maintained it has been “doing a lot of engagement, particularly with the airlines with a larger share [of flight routes] upfront,” which it expects to continue throughout the trial. 

Although the partners acknowledged that hundreds of flights would need to be deviated to obtain a high level of statistical significance, ATI CEO Gary Elliot stated he is confident the study will generate “real-world evidence at an unprecedented scale” with which to inform future potential policy decisions.