Reduced Lateral Separation Minima (RLAT or RLatSM), is an aeronautical flight term identifying the reduction from standard lateral separation minima between aircraft to a lower amount deemed safe, first introduced on the North Atlantic in December 2015 for the North Atlantic Tracks.
Beginning in 1961, the North Atlantic Organised Track System (NAT-OTS) was created, wherein specific routes were defined daily in order for pilots to safely and efficiently fly across the North Atlantic between Europe and America.
RVSM allowed more aircraft to operate on the same route, thereby improving fuel efficiency and performance.
[1] RLAT was introduced on a trial basis on 12 November 2015, with the first tracks published on 13 December 2015.
After March 28, 2018, ICAO combined the Rlat and RLong program into one- the Performance Based Communication and Surveillance (PBCS).