First, you need to know the technique used to fly in Dalaran. Read this post, it explains it in detail:
http://www.mmowned.com/forums/world-...explained.html
Using the same method from above, you can fly in Wintergrasp during the 'Battle for wintergrasp' and avoid getting the 'no flying' debuff. This also means you wont be kicked out if you land and fight, using this method.
Here is a spot that will work:
You start off in the Icecrown Zone, which is the bottom right of this picture. From a hover, fly into wintergrasp until you see the red text in the middle of the screen indicating you entered wintergrasp. At this point you should be below the 'sky zone' of wintergrasp. Flying upward and entering the 'wintergrasp sky zone' does not give a message, you just have to guess. After that, fly down and re-enter the Wintergrasp 'no fly zone' (indicated when you see the time remaining and sieges at the top middle of the screen). If you made it that far without a debuff or 'kick you out' message, you are good to fly around in the no fly zone.
As with dalaran, you MUST pass through the invalid zone before entering the sky zone.
If you have a multi person flying mount, you can carry people inside the fortress to harass from the top of walls/workshops.
If wintergrasp is full and you didn't get accepted in, you can still play in wintergrasp without getting the 'exit wintergrasp' warning.
- Dying or being near a workshop when it flips factions will give you the wintergrasp full message.
- Making and driving sieges does not kick you out.
Credit to Infernon for proving it is possible to do this in wintergrasp.
good luck