New North Atlantic Reduced Lateral Separation Minimum (RLatSM)


New North Atlantic Reduced Lateral Separation Minimum (RLatSM)

Jimmy Gadallah | - 02/11/2016
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Planning and Operating
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It’s crucial for all operators to fully understand a new Reduced Lateral Separation Minimum (RLatSM) in North Atlantic Airspace.

Advancements in aircraft avionics and air traffic management flight data processing systems began analysis of whether the lateral separation standard in the current North Atlantic (NAT) minimum navigation performance specification (MNPS) airspace can be reduced to increase the number of tracks available and thereby increase capacity at optimum flight levels. On February 5, Gander, Shanwick and Reykjavik area control centres (ACCs) commenced participation in the trial of a 25 nautical mile (NM) reduced lateral separation minimum (RLatSM) in portions of their oceanic control areas (OCAs).


Track spacing for MNPS approved aircraft is currently one degree of latitude, which equates nominally to 60 NM. The proposed change will reduce lateral separation for aircraft operating at the flight levels and tracks associated with the NAT Region Data Link Mandate airspace, which can be practically achieved by establishing tracks which are spaced by ½ degree of latitude. This track spacing initiative will be referred to as Reduced Lateral Separation Minimum (RLatSM).


RLatSM will be implemented on a phased basis. The first phase will introduce ½ degree spacing between the two core tracks of the NAT organized track structure (OTS) from FL350 to FL390 inclusive. Phase Two will then expand the implementation throughout the entire NAT OTS. This will take place at yet to be determined dates. Finally, Phase Three will encompass the entire ICAO NAT Region, including for converging and intersecting track situations.

Operator Eligibility and Participation

Operators don’t need to apply to be part of the trial and will be eligible to flight plan RLatSM tracks provided the flights are:

  • MNPS and RNP4 approved
  • ADS-C and CPDLC equipped and authorized (where applicable)
  • Required CNS systems are operational

Flight Planning

The majority of business aircraft fly above the tracks at 43,000 feet or higher. This new spacing only applies to flight levels 350 to 390 inclusive. Some operators have reported to the International Operators Committee that the Gander Centre will not assign routes with half-degree waypoints unless operators make a specific request in their flight plan.

The North Atlantic is the world’s busiest oceanic airspace and it’s not uncommon for business aircraft operators to file flight plans that overlay the tracks from above so they can take advantage of the best winds. Even if operators fly above the tracks, they need to have a plan to get down between the tracks should the aircraft lose an engine or pressurization. That said, flying with a half degree of separation requires an increase in the crew’s overall situational awareness at every point along the route, particularly in reference to where the tracks are in comparison to the aircraft’s position in case a diversion is necessary.

As a trusted 3rd-party service provider, UAS can assist operators in planning via the RLatSM within the North Atlantic region, special considerations are however needed to ensure that the below equipment codes are present in the ICAO flight plans submitted.


ATS systems use Field 10 (Equipment) and Field 18 (Other Information) of the standard ICAO flight plan to identify an aircraft’s data link and navigation capabilities.
The operator should insert the following items into the ICAO flight plan for FANS 1/A or equivalent aircraft:

Field 10a (Radio communication, navigation and approach aid equipment and capabilities):
• Insert “J5” to indicate CPDLC FANS1/A SATCOM (Inmarsat) and/or “J7” to indicate CPDLC FANS1/A SATCOM (Iridium) data link equipment
• Insert “X” to indicate MNPS operational approval

Field 10b (Surveillance equipment and capabilities);
• Insert “D1” to indicate ADS with FANS 1/A capabilities

Field 18 (Other Information):
• Insert the characters “PBN/” followed by “L1” for RNP4

Flight crews must report any failure or malfunction of GPS, ADS-C or CPDLC equipment to air traffic control (ATC) as soon as it becomes apparent.

Our Sources 

The current, updated versions of the Draft NAT RLatSM Plan and associated documents are provided on the ICAO EUR/NAT website (, via the links to EUR & NAT Documents >> NAT Documents >> Planning documents supporting separation reductions.