NAT Contingency Procedures and SLOP Explained

Two procedures are used to manage risk over the ocean: contingency procedures, for when something goes wrong and the crew cannot get a clearance, and the strategic lateral offset procedure (SLOP), which is used every day to reduce the risk of collision.

Contingency procedures

• They apply when an ATC clearance cannot be obtained.
• If a clearance to deviate is received, the revised clearance supersedes all the contingency provisions and must be followed.
• The ICAO bulletin on oceanic errors tells crews that when a clearance is not available, they apply the 5 NM lateral offset contingency procedure and inform ATC.
• The full procedures are in the PANS-ATM (Doc 4444), the NAT Regional Supplementary Procedures (Doc 7030) and chapter 13 of NAT Doc 007. Procedures are revised from time to time, so always use the current editions.

Strategic lateral offset procedures (SLOP)

• SLOP spreads aircraft sideways along a route or track, so they are not all exactly on the centreline.
• Only offsets to the right are authorised, in tenths of a nautical mile up to 2 NM.
• SLOP is authorised in the NAT airspace, and it is not the same as a weather deviation.
• The ICAO bulletin warns crews not to start a SLOP close to a waypoint, because the offset can cause the waypoint to be skipped.

This is a summary only. Use current ICAO documents and your operator's procedures.

Open the oceanic clearance guide

FAQ

Is a left offset allowed under SLOP?

No. Only right offsets are authorised.

What is the difference between contingency procedures and SLOP?

SLOP is a routine offset used to reduce collision risk. Contingency procedures are for abnormal situations when a clearance cannot be obtained.

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For training and reference only. Check official sources before any real flight.