Guidance concerning Air Navigation in and above the NAT MNPSA
consecutive eastbound and westbound minimum time tracks are seldom identical. The creation of a different organised track system is therefore necessary for each of the major flows. Separate Organised Track System (OTS) structures are therefore published each day for eastbound and westbound flows.
The construction of these OTS structures is accomplished through a formal process of
cooperation between ATC and the operators. Details of this process are explained in Section 2.2 above. The resulting structures are published (twice each day) in the form of a “NAT Track Message” via the AFTN. This Message and its correct interpretation are detailed above in Section 2.3 and examples are shown at the end of Chapter 2.
If orientation/location of the published OTS structure appear to be appropriate for the origin
and destination of a particular flight, then the operator is encouraged to flight plan the NAT route segment
via one of the published tracks. Currently about half of NAT flights utilise the OTS.
Use of OTS tracks is not mandatory. The orientation/location of the published OTS may not
be appropriate for the origin and/or destination of a particular flight. A NAT route segment that does not follow a published OTS track, in its entireity, is known as a “Random Route”. Aircraft may fly on random routes which remain clear of the OTS or may fly on any route that joins or leaves an outer track of the OTS. There is also nothing to prevent an operator from planning a route which crosses the OTS. However, in this case, operators must be aware that whilst ATC will make every effort to clear random traffic across the OTS at published levels, re-routes or significant changes in flight level from those planned are very likely to be
necessary during most of the OTS peak traffic periods.
Outside of the OTS periods operators may flight plan any random routing, except that during
the hour prior to each OTS period some additional restrictions apply. These are detailed in Section 4.1.6
Adjacent Airspace, Route Structures, Links & Constraints
A large majority of flights through the NAT MNPS Airspace enter and/or leave it via the
European and/or North American Regions. To facilitate these busy flows of traffic, various transitional airspaces and linking route structures have been established in and through the adjacent EUR and NAM areas. These are described in Chapter 3 above. Of particular significance are the NAR, NER, NOROTS and the US East Coast Link Route structures. Details of these routes and their associated procedures are contained in the AIS of the relevant authorities and/or via their websites. The necessary Internet Links to obtain this information are listed above in Chapter 3. Account must be taken of these route structures in planning any flight through the NAT Region that starts or ends in either or both of the European and North
Altitude & Speed
During the OTS Periods (eastbound 0100-0800 UTC, westbound 1130-1900 UTC) aircraft
intending to follow an OTS Track for its entire length may plan at any of the levels as published for that track on the relevant current daily OTS Message. Aircraft following a “random route” (see above definition) or flying outside the OTS time periods, should normally be planned at flight level(s) appropriate to the direction of flight. (Note: “Appropriate Direction Levels” within the NAT MNPSA are specified by the Semi-circular Rule Per ICAO Annex 2, Appendix 3, Table a). Planners should note however that the NAT Provider State AIPs specify some exceptions to use of “Appropriate Direction Levels” both during the OTS
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