Harman Patil (Editor)

Reduced lateral separation minima

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Reduced Lateral Separation Minima (RLAT or RLatSM), is an aeronautical flight term identifying the reduction from standard separation minima between aircraft to a lower amount deemed safe, first introduced on the North Atlantic in December 2015 for the North Atlantic Tracks.



The forerunner of RLAT/RLatSM is RVSM - Reduced Vertical Separation Minima - first introduced in 1997, reducing the standard altitude spacing between aircraft from 2,000 feet to 1,000 feet. RVSM allowed more aircraft to operate on the same route, thereby improving fuel efficiency and performance. On the North Atlantic the concept of reducing the standard lateral separation was discussed at NAT SPG meetings as far back as the 1960s. The successful implementation of RVSM and also a Reduced Longitudinal Separation program allowed progress on the RLAT issue.

Introduction in 2015

RLAT was introduced on 12NOV2015, with the first tracks published on Monday 13 December 2015. The key changes are: a reduction in separation to ‘half-track’ compared to the existing structure, introduction of 24 new Oceanic Entry Points (OEP’s), and some procedural changes. These will affect all operators on the North Atlantic.

Track Design

RLAT Tracks will ‘sit into’ the existing track structure RLAT Tracks are FL350 to FL390 only Phase 2 of the Trial will extend the RLAT minima to all tracks between FL350-FL390, estimated implementation date May 2016.

Aircraft Requirements

Since the RLAT Tracks will always be within MNPS (Minimum Navigation Performance Specification) airspace, operators must meet the existing basic MNPS requirements, and the additional RLAT requirements. Existing requirements:

  • HF Radio
  • MNPS (2x LRNS, Aircrew MNPS approved)
  • To use RLAT Tracks:

  • Comms: CPDLC
  • Nav: RNP4
  • Surveillance: ADS-C
  • There are no changes to the in flight contingency procedures and weather deviation procedures as detailed in PANS ATM Doc444 Para15.2 & 15.2.3. SLOP procedures are also unchanged.


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