BN, as I pointed out on another thread, there is an evident issue with how the AI plans the taxi routes and determines if they are clear or not. Manual says that if a route isn't clear the AI will leave the mission (despawn), but that doesn't happen right now. AI will go and crash or go through (depending on whether is static or not) even in the missions created by default with correct places used. You may need to take a look at this, there is something going on.