Certain maps will be flagged as countries with restricted air-space. What this means is that, when you enter one map (an 'edge' map), you are greeted by fighter jets that fly by and tell you to turn back. If you proceed to fly further into the territory (go to the next restricted map), you are forced into combat with these air craft. The original air craft the party earns isn't built for combat, you will only fight a losing battle and get shot down. Later air craft will come with better combat capabilities

While my world probably will have random traffic (planes and birds flying by, occasional boats in the water, truck on the road, etc) some of the 'random' traffic won't be random at all. In fact, sometimes NPCs will give you ironic info on things that you should follow. For instance, a lady in a random park somewhere will comment "while the ducks fly south for the winter, for some reason Baby Harpies seem to always fly North. I wonder where they all go to."

Not all random traffic leads to something, but chances are if you can follow it onto the next map, its most likely there to lead to somewhere important. To make things even tougher, you must go from map to map within a certain period of time which is sometimes impossible without the proper vehicle(s).