Players can't initially fly in World of Warcraft's Legion expansion, but once they have reached level 110 and made a few friends they can at least call a flying cab.
The Flight Master's Whistle is an item players receive upon completing a relatively easy level 110 faction quest, Uniting the Isles. Once you're friendly with all five main Broken Isles factions you unlock World Quests and are awarded a whistle that will summon an instant ride from wherever you are in-game (outdoors, I imagine) to the nearest static flight point on the map.
Blizzard's decision to barricade the ability to use flying mounts in the new zones behind an extensive series of exploration and faction-grinding tasks, something introduced after the uproar over the lack of flying in the previous expansion, is fine by me. I love the tension and excitement of exploring the new lands without knowing I can fly to safety at any given minute. But it is nice to know Broll Bearmantle and I can always thumb a ride home in a pinch.