In a continuous effort to mitigate the risk of traffic conflict caused by non-normal events (i.e. aircraft navigation errors, height deviation errors and turbulence induced altitude-keeping errors), arrives an amendment to SLOP within the release of NAT Doc 007 v.2019-3.  With the density of traffic only increasing in the NAT, provisions needed to be made that would further reduce the risk of conflict when leaving an assigned track.

NAT Doc 007 v.2019-3 now specifies the adoption of “micro SLOP” in the NAT; which allows for aircraft to fly up to 2NM right of track but at 0.1NM increments.  Performing these offsets in 1/10th of a nautical mile increments will reduce the risk of traffic conflict, adding an additional safety margin. Given the possibility for delay in ATC intervention, aircraft are encouraged to fly self-selected lateral offsets.  By adding provision for 0.1NM offsets, authorities have significantly reduced the risk of collision for those aircraft that apply these new SLOP standards.

What this means for us?

  • Flying an offset SLOP position still requires no ATC involvement and is an option for the pilot-in-command
  • SLOP offsets are only right of centerline and up to 2NM using 1/10th NM increments
  • Any offset left of track requires ATC notification and is not permitted as part of SLOP
  • Aircraft without automatic offset programming capability must still fly centerline
  • When choosing an offset, flight crews should coordinate with other aircraft on 123.450 MHz to minimize wake turbulence
  • SLOP shall still not be applied below FL285 in the Reykjavik CTA or Bodo OCA
  • The new provisions which allow the use of 0.1NM SLOP to the right of centerline up to 2NM, align with all other current ICAO provisions
  • These new SLOP procedures are applicable as of July 2019


Written by Wesley Scott 8/15/2019