45N040W NATH DOVEY
This particular NATH is a "stub track" where NY Oceanic
identify a demand in their FIR which Shanwick Oceanic
, (as the 'designers' of the Westbound OTS; Gander Oceanic
designing the Eastbound), do not; therefore a half or "stub track" is designed from 40W purely to provide for the needs of NY Oceanic
as identified by them.
exits from NY Oceanic
into the Atlantic High
area of US airspace, and not Canadian airspace, which as I said previously is usually too far north for Florida destinations. (Not that they would never route into Canadian airspace, it is just that the weather usually means they are able to route farther south and closer to the 'Great Circle
The weather determines everything in terms of routes in the NAT area. You are probably already aware that as the prevailing wind in the Northern Hemisphere is westerly, those flights coming eastbound will look to pick up a strong tailwind component, increasing their groundspeed, reducing flight times and saving fuel/€/$/£... Going westbound however, a reduced headwind component is required to avoid a significant fuel/time penalty, therefore those westbound flights will prefer to route via areas where the westerly wind is at its lightest.
Operators have sophisticated computer sustems such as Lufthansa's LIDO
which calculate routes between destinations on a daily basis on the basis of forecast MET, ATC route charges, ATC flow control regulations, position of the NAT OTS, position of Jetstream, Great Circle, airspace closures due to military activity/industrial action, shortest flight time due to weather, most fuel economic based upon NM flown, etc. etc. A EDDF to KJFK route for example will therefore be different every day due to the variables involved in calculating the optimum route.
Oceanic "Random" routes, as with all other routes, are created by the operator's FPL department using systems such as LIDO, and are then submitted to ATC who, provided any regulation/rule applicable to a specific route has been met, accept that FPL. ATC doesn't get too involved in the production of a FPL except to identify to an operator if a particular rule or regulation associated with a route has not been adhered to. The operator will then simply resubmit the corrected FPL.
The reason I'm familiar with the routes is that as an Oceanic controller I see them at work every day...
Just checked out that website FlightAware > British Airways (BA) #253 Flight Tracker
which reminded me of another factor - ETOPS