January 15, 2018

Increasing operational flexibility in the North Atlantic

Increasing operational flexibility in the North Atlantic

Since December 2015, some aircraft tracks over the North Atlantic (NAT) Region have been spaced closer together as part of a project to increase airspace capacity, cut fuel burn and reduce carbon emissions. The project – called Reduced Lateral Separation Minimum or RLatSM – is an ICAO initiative being jointly introduced by NAV CANADA and NATS, the UK air traffic services provider.

Why reduce lateral separation?

The North Atlantic is the busiest oceanic airspace in the world, with most aircraft following tracks that are set each day based on the traffic demand and prevailing weather conditions such as the jet stream. These tracks are known as the Organised Track System (OTS). As ATS surveillance and direct controller pilot communications are unavailable in most parts of the NAT, the OTS provides the airspace structure to ensure efficiency and safety.

The tracks are normally separated by one degree of latitude, which is the equivalent of 60 nautical miles. This large horizontal separation limited options for aircraft crossing the North Atlantic and caused airspace congestion, particularly during peak hours.

Introducing RLatSM

Phase 1 of RLatSM consisted of the introduction of an additional track (track C in the example below), thus reducing the separation minimum to 25 nautical miles. All flights operating between flight level (FL) 350 (35,000 ft) and FL 390 (39,000 ft) inclusive on the three RLatSM tracks (tracks B,C,D in the example below) within the Gander and Shanwick oceanic control areas since December 15, 2015 have participated in the trial.

Photo: NATS

With the successful completion of the first phase of RLatSM, we recently launched Phase 2 which expands the number of tracks that are spaced by one-half degree beyond the core tracks of the OTS. The image below shows the tracks from January 5th, where tracks B,C, & D and E,F, & G are separated by the new minimum of 25 nautical miles.

So what does this mean for those who fly the NAT OTS? Getting more planes into the most efficient paths means savings in terms of time as well as fuel. These savings translate to a decrease in costs, but also in a reduction in environmental impact. With phase 2 now implemented,  reduced lateral separation will save an estimated 52,000 tonnes of carbon a year, the equivalent of 14,000 transatlantic flights.

Only those operators/aircraft eligible for RLatSM operations will be allowed to operate on designated RLatSM tracks between FL 350 and FL 390 (inclusive). Operators are eligible to flight plan RLatSM tracks provided the flights are:

  1. Required navigation performance 4 (RNP 4) approved
  2. Automated dependent surveillance-contract (ADS-C) equipped; and
  3. Controller-pilot data link communications (CPDLC) equipped.

The required communications, navigation and surveillance (CNS) systems must be operational and flight crews must report any failure or malfunction of GPS, ADS-C, or CPDLC equipment to air traffic controllers as soon as it becomes apparent.

Space-based ADS-B   

The launch of Aireon’s  space-based ADS-B technology will further increase flexibility both on the NAT OTS and in the NAT Region overall. With real-time global air traffic surveillance coverage there will be more dynamic access to better flight profiles and an opportunity to further decrease RLatSM from 25 nautical miles to approximately 15 nautical miles. More information on the NAT RLatSM plan is available on the ICAO website here.


RLatSM has been a long time coming and its good to see the customer reaping benefits from suitably equipped aircraft. One issue which comes to mind is how is the extra traffic on the NAT tracks impacting the domestic interfaces on either side of the NAT. Has capacity increased in domestic EU and NAM airspace to enable aircraft to depart on time and receive their optimum track. It will be interesting to know, since the introduction of Phase 2, whether there is an increase of aircraft receiving their planned track and flight level.

I watch with great interest the devolpments in North Atlantic reduced separation standards. It was a pleasure to have worked on this from 2009-2015 for NAV Canada and seeing it continue to progress is exciting. Getting to the end game of what can be accomplished through ADSB will have it challenges of course, but my hat is off to the great work being done by NAV, other ANSPs and the customers.

This system is totally epic guys

this is epic

As a B777 captain who has operated flights regularly on the North Atlantic for many years, more frequently it seems now during the summer months, that flights are requiring to deviate from the ATC cleared NAT for weather avoidance. Other than or in addition to the ICAO SOP’s associated with weather deviations on the NAT’s are there any other helpful suggestions, which could serve to enhance the best communications possible between aircraft and the oceanic sector being operated in under these circumstances? Sometimes weather deviations can be imminent, with very little time, where it is not always possible to obtain a clearance prior to the required deviation to maintain and ensure flight safety.


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