Moving away from a square which is within threatening reach of an enemy, provokes OA if one does not shift, is pushed/pulled/slid or teleports.
Further, so far I know, squares are 3d, as indicated here as well (jump over an enemy): http://community.wizards.com/content/forum-topic/2623551
Let's say I have an enemy directly in front of me. When I fly one square upwards, I leave the square adjacent to the enemy I stand on and therefore provoke OA. When flying one square higher, I actually provoke OA again (they can't hit me twice during the same turn, I know) because I leave that adjacent square which is diagonally top/front of the enemy.
I now look at the monk power "Whirlwind Kick" which says as a movement action: "You fly your speed. The first square of this movement doesn't provoke Opportunity Attacks." When I consider the above stated situation, the enemy could attack me with an OA when leaving the diagonal adjacent square (if I don't fly backwards first, but this won't work if there is an enemy behind me). Assuming that the idea behind this movement action is to get away after gathering enemys around yourself and assuming there is an enemy behind you as well, this won't work because you leave adjacent squares twice but only the first square doesn't provoke OA.
Can you please tell me if my understanding of 3d squares and OA is correct and if so, if there is a possibility to fly away from several adjacent enemies using the mentioned monk movement action?