A few years back whilst traveling LGW to Puerto Plata on a Britannia 767 I visited the flight deck. When I asked which North Atlantic Track (NAT) we were on the captain said that we were not on one.
Instead the crew had suggested THEIR OWN route and that this had been approved. He said it was a GPS track.
I was under the impression that all north Atlantic crossings routed via the NAT tracks e.g. Track A, B, C, D etc westbound and Track U, V, W, X, Y, Z eastbound.
Any other pilots out there have any answers?