Here's a little info on where and how to fly over anything in Ter Mur.
First, you must be a gargoyle, and be in flying mode. For scripts, use event macro 60. Now, just as roads and highways are restrictive to certain places and locations with borders, so is it also in Ter Mur. These "Flyways" as I call them are much like bridges or roads. They only go to certain locations and at certain points along the flyways, your gargoyle can jump off and proceed about the land, or be restricted onto the flyway due to geographical obstacles, such as mountains, water or void areas. Should you decide to leave the current flyway, you cannot get back on from where you left. You must return to a 'launch tower' to get back on the flyway. Below is an image of what I call a "Launch Tower." These buildings are placed around Ter Mur and serve as 'airports' for gargoyles to enter and exit a flyway.

Each tower has a set of sparkles that designate the beginning of the flyway. Respective to the UO radar, if a sparkle pair resides on the east wall of the tower, the flyway goes in that direction. The map below shows Ter Mur with the launch tower locations circled, and the flyways connecting them all.

Additionally, purple circles are the 'passes' where only gargoyles can fly through. Some are water, and some are mountains.
While you are on the flyway, NO monsters can attack you unless a monster is on the launch tower. One more thing, at the moment you take to the air, EasyUO sees your gargoyle as poisoned. Razor also sees and sets your health bar to orange. I've attached the Ter Mur map for anyone who wants it, it is rather large, but is a good refrence.
Enjoy!
SS