Midnight Flight Master

The Howling Ridge, Voidstom flight point is unlocked after completing the quest Domus Penumbra (Establish your base at the Howling Ridge)
Just do the main story line for Voidstorm and you will get to the required quest.
Completing the quest will make [npc=235703] appear.

Waypoints for each zone:

Isle of Quel'Danas:
/way #2424 57.58 33.80 Terrace of the Sun

Eversong Woods:
/way #2395 44.68 44.99 Fairbreeze Village
/way #2395 47.78 67.17 Tranquillen

Zul'Aman
/way #2536 39.91 40.94 Atal'Aman
/way #2437 33.89 78.34 Torntusk Overlook
/way #2437 44.84 65.41 Amani'Zar Village
/way #2437 44.01 33.63 Shadebasin Watch
/way #2437 47.30 25.53 Camp Stonewash
/way #2437 38.88 23.20 Witherbark Bluffs

Harandar:
/way #2576 70.77 52.97 The Den (Behind the Waterfall)
/way #2413 69.39 52.56 Har'athir
/way #2413 64.60 23.20 Har'kuai
/way #2413 35.53 23.77 Har'mara
/way #2413 31.74 67.44 Har'Alnor

Voidstorm:
/way #2405 51.14 69.25 Howling Ridge (Requires completion of Domus Penumbra Campaign quest)
/way #2405 42.27 73.71 Locust Point
/way #2405 36.91 58.96 The Ingress
/way #2444 38.13 79.94 Master's Perch

The Den flightmaster is underground beneath the building. Go through a waterfall and he's there.