The OCC position is responsible for maintaining required separation within the Oceanic Control area by using the position reports. OCC shall also approve/deny all requests for altitude and/or speed changes.

IvAc shall only be used to communicate via text to other pilots and controllers.

The OCC shall process and approve all oceanic clearances.


Minimum separation:


Minimum vertical separation within MNPS airspace is 1,000 feet up to and including FL410, and 2,000 feet above that.

Supersonic flights require 4,000 feet vertical separation from all other traffic if no other form of separation exists. This applies at any level for aircraft at supersonic speeds.


Minimum lateral separation is sixty (60) Nautical Miles.
Parallel tracks which are spaced apart by one (1) degree, and which change latitude by no more than two (2) degrees over a longitude of ten (10) degrees are deemed to be separated.

Example: tracks from 50N020W to 52N030W and 49N020W to 51N030W are separated. 52N010W to 55N020W and 51N010W to 54N020W are not separated.

NATs are normally defined so that they do not change latitude by more than 2 degrees for each 10 degrees longitude difference thereby ensuring separation.


Minimum longitudinal separation for aircraft on the same track is ten (10) minutes flying time.

Example: An aircraft passing 49N040W at FL380 must not be followed by another at the same level on the same track until ten minutes have elapsed after the first one passed that point.

Aircraft on crossing tracks at the same level must be fifteen (15) minutes apart at the point where their tracks cross.

Speed differences:

Aircraft with different speeds on the same track/FL will gradually get closer or further apart. It is imperative to monitor this change of spacing closely for loss of separation. Aircrafts are requested to maintain the cleared speed given with the oceanic clearance.

When calculating initial spacing use the following formula: Slow followed by fast: Add one (1) minute to the standard for every increase of 0.01 Mach number of the second aircraft.

Example: M0.80 followed by M0.84 requires FOURTEEN minutes at ocean entry same track same level.

Fast followed by slow. Subtract one (1) minute from the standard for every decrease of 0.02 Mach number of the second aircraft. The minimum is 5 minutes at Oceanic entry.

Example: M0.84 followed by M0.80 requires a minimum of EIGHT minutes separation at ocean entry same track same level.

If two aircraft at different speeds are entering Oceanic Airspace at the same point but following tracks which will be separated by no less than sixty (60) nautical miles, or ten (10) degrees of longitude after entry the increase above is not required. The reduction above may still be applied.

If this situation occurs inside Oceanic Airspace (as opposed to at entry) then they are considered to be on crossing tracks and the fifteen (15) minute rule applies. There is no reduction to the fifteen minute rule for fast followed by slow on crossing tracks.

Opposite direction:

The following is included in order to determine the separation requirement for aircraft wishing to climb/descend through the level of another aircraft opposite direction, whether on the same track or crossing tracks opposite direction.

Vertical separation must be established by a position calculated to be thirty (30) minutes flying time before the position/time at which it is estimated that they will pass one another, and must continue to exist until 30 minutes after they are estimated to have passed. If it can be positively established that they have passed, by both having reported passing the same Oceanic Reporting Point then the separation may be reduced to 10 minutes after they are known to have passed each other.

Example: Two aircrafts,
A: routing 55N010W 56N020W 57N030W
estimates 56N020W at 1234Z and 57N030W at 1304Z
B: routing 56N030W 56N020W 56N010W.
estimates 56N030W at 1224Z and 56N020W at 1254Z.

Inspection and calculation indicates that they will both be approximately one third of the way from 20W to 30W (or two thirds of the way from 30W to 20W) at approximately the same time (1244Z). So vertical separation must exist from 1214Z until 1314Z. Once (B) has reported coordinate 20W the pass will have been established and one or other may climb/descend through the other aircraft’s level after 1304 (ten minutes after they are known to have passed).



SELCAL shall be used whenever aircraft are equipped. On initial call-up SELCAL should be verified. Subsequent communications shall always be initiated with a SELCAL signal.

SELCAL watch on the assigned frequency should be maintained even in areas of the Region where VHF coverage is available and used for air / ground communications.
Normal SELCAL service is available on HF General Purpose 127.900 (12790.0 kHz).

To transmit a SELCAL signal enter .selcal [callsign] in the IvAc comm. box and transmit. If the SELCAL check fails the aircraft should be advised to monitor the frequency continuously.


SSR Codes:

Unless otherwise directed by ATC, aircraft equipped with SSR transponders in North Atlantic Flight Information Regions, shall operate transponders continuously on mode A code 2000 regardless of direction of flight except that the last assigned code shall be retained for a period of 30 minutes after entry into NAT airspace.

NOTE: This procedure does not affect the use of special purpose codes 7500, 7600 and 7700 in cases of unlawful interference, radio failure or emergency.


The Strategic Lateral Offset Procedure (SLOP) is now a Standard Operating Procedure throughout the North Atlantic (NAT) Region. This procedure mitigates collision risk and wake turbulence encounters. Pilots conducting oceanic flight within the NAT Region with automatic offset programming capability are recommended to fly lateral offsets of either 1 or 2 NM of centre line.

The introduction of very accurate aircraft navigation systems, along with sophisticated flight management systems, has drastically reduced the number of risk bearing lateral navigation errors reported in NAT airspace. Paradoxically, the capability of aircraft to navigate to such a high level of accuracy has led to a situation where aircraft on the same track but at a different levels, are increasingly likely to be in lateral overlap. This results in an increased risk of collision if an aircraft departs from its cleared level for any reason.

SLOP reduces risks by distributing aircraft laterally. It is applicable within the New York Oceanic, Gander Oceanic, Shanwick Oceanic, Santa Maria Oceanic, Sondrestrom and Reykjavik Flight Information Regions, and within the Bodo Oceanic Flight Information Region when flights are operated more than 185KM (100NM) seaward from the shoreline.

SLOP conforms to direction in the International Civil Aviation Organization’s (ICAO) Procedures for Air Navigation Services – Air Traffic Management (PANS-ATM, Doc. 4444, 15.2.4) and is subject to the following guidelines:
Aircraft without automatic offset programming capability must fly the route centre line.

Operators capable of programming automatic offset may fly the centre line or offset one or two nautical miles right of centre line, allowing for 3 possible positions along route. Offsets are not to exceed 2NM right of centre line and offsets to the left of centre line are not permitted. An aircraft overtaking another aircraft should offset within the confines of this procedure, if capable, so as to create the least amount of wake turbulence for the aircraft being overtaken. The pilot should take into account wind and estimated wake vortex drift and time to descend. (Nominal descent rates for wakes are 300-600fpm).

Pilots should use whatever means is available (e.g. TCAS, communications, visual acquisition) to determine the best flight path to fly. Pilots may contact other aircraft on frequency 123.45MHZ, as necessary, to coordinate the best wake turbulence offset option.

Pilots may apply an offset outbound after the Oceanic Entry Point and must return to centre line before the Oceanic Exit Point. Position reports transmitted via voice should be based on the waypoints of the current ATC clearance and not the offset positions.
Aircraft transiting Oceanic Radar Areas may remain on their established offset positions.

There is no ATC clearance required for this procedure and it is not necessary that ATC be advised.


Radio frequencies:

All communications take place HF frequencies. As the current pilot/controller software doesn’t support HF frequencies a modified decimal system has been arranged where the frequency 12237 kHz is entered as 122.37 in IvAc. Phaseology for the said frequency remains “one two two three seven kilohertz”


Communication with aircraft:

Communication with aircraft over the North Atlantic in real life are made by relay through the FSS stations. For the simulation purposes we will omit that fact and the radio operator and controller work is done by the same person.