There's safety restrictions for flight paths - in case of sudden engine failure, you want the plane to be able to glide to an airfield or other inhabited areas that you can get rescued from.
I'm also not familiar enough with air-traffic control rules in the area to be sure, but it looks like you'd have to either pass through Icelandic or Scottish airspace to get to Scandinavia.
> I'm also not familiar enough with air-traffic control rules in the area to be sure, but it looks like you'd have to either pass through Icelandic or Scottish airspace to get to Scandinavia.
There's two separate issues there: there's airspace controlled by the Iceland and the UK and there's sovereign airspace. In the case of the UK and Iceland, the airspace they control goes far beyond the sovereign airspace.
the G-V is certified for ETOPS -- extended twin-engine overwater operations. Second, there's no "gliding" involved. ETOPS flight plans are designed for single engine operation. That floating seat cushion is for when both engines fail.
That makes sense but there are so many transpacific routes that spend huge stretches of time over open water that I am not sure it is even feasible for all commercial flights. CIA SAD/SOG operations likely have a much broader risk envelope.
Further brief research suggests it's "flight time with one failed engine" that's a constraint, somewhere between 60 and 180 minutes, depending on how the plane is certified. The Gulfstream 5 is a twin-engine aircraft, which makes it more awkward for crossing large bodies of water. For long-distance flights, you're more likely to be on a four-engine plane, which has more lenient safety margins in case of engine failure.
That said, the Pacific has a good chunk of diversion airports available as well.
I'm also not familiar enough with air-traffic control rules in the area to be sure, but it looks like you'd have to either pass through Icelandic or Scottish airspace to get to Scandinavia.