Oceanic Time Restrictions

[Paulmc98]

Can an interval restriction option be added to the possible time restrictions that can be imposed on an aircraft?

At present the system assumes all aircraft are passing accurate time estimates. I hope my explanation below outlines why an interval would be superior to the current system.

Current system:
Both aircraft cleared to cross at the same FL and OAP -
ABC123 passed an estimate of 1200 but is actually estimating at time 1203.
XYZ987 passed an estimate of 1202 but is actually estimating at time 1204. 3 minutes is required behind ABC123 so a NBT of 1203 is imposed.

So the time over for both would be:
ABC123 - 1203
XYZ987 - 1204

Only 1 minute separation with XYZ987 having the possibility of crossing at time 1203 providing no separation.

My proposal:
ABC123 passed an estimate of 1200 but is actually estimating at time 1203.
XYZ987 passed an estimate of 1202 but is actually estimating at time 1204. 3 minutes is required behind ABC123 so an interval of "ABC123 +3" is imposed on the pilot.

This interval restriction is not sent to the pilot but rather to the domestic controller so that they can apply the NBT time.

As ABC123 is estimating at time 1203, the domestic controller would apply a NBT of 1206 on XYZ987 which would be passed by VHF coms inside the domestic sector.

If the estimate of ABC123 slips by a further minute (to 1204) the domestic controller can then further delay XYZ987 by providing a new NBT of 1207.

Potential issue
What the interval time assumes is that the time is to be applied at a common oceanic entry point in both flight plans.

If for example a conflict is probed between an aircraft entering the ocean from the Shannon FIR which is required to be restricted behind an aircraft entering from the Scottish or Brest FIR, Shannon would not have an accurate boundary estimate for the lead aircraft. It would then be the responsibility of the oceanic controller to apply an NBT or NLT for the aircraft entering behind from the Shannon FIR.