2 sheds
Agree with the sentiment, but not fully with what you say. Remember we're talking time here and not distance. So at 1210, the faster aircraft
IS 10 minutes flying time from the slower aircraft and will remain so until 1220. After that the separation will erode, but not before.
We use a sliding Mach number technique to cater for such situations over the Atlantic. By applying a relevant time interval based on the aircraft's speeds, you should have the standard 10 minutes separation when the second aircraft pops out the other side of the pond.
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10 West
UK ATC'er
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