WoW Insider writes:
"Finally, we come to the end. Icecrown is the very last zone in Wrath, and a very gloomy one it is (in my opinion). This zone, as well as Storm Peaks, was designed with flying mounts in mind, but like Storm Peaks it still has flight paths for those of us who prefer to travel on autopilot. And like Zul'Drak, all the flight paths are neutral, being controlled by either the Argent Crusade or the Knights of the Ebon Blade.
Unlike either of those zones, however, the FPs in Icecrown are extensively phased. Only the first, Argent Vanguard, is accessible immediately upon entering the zone, so don't go cruising around trying to pick up all the FPs. Just go through the normal quest lines and you'll unlock all four of them sooner or later."