ai_baseflyergeneric

This entity is not in the FGD by default.
It should not be put directly in a map because it does nothing.

ai_baseflyergeneric is a point entity available in Black Mesa. This is flying NPC which is a base class for flying NPCs like npc_ichthyosaur, npc_alien_controller, etc. Instead of using Valve's flying code, the programmers wrote their own class to handle the movement for such type of NPCs. This NPC can't use model and doesn't do anything, although other NPCs still can attack it. Does not provide unique inputs and outputs.

Quote from this video:

With an all new fly class we where able to control how we wanted each of these NPCs to move through the air and attack. You will find a video below demonstrating the work in progress controller movement with his attacks disabled. As you can see, the controller will be constantly moving around the player to keep the player on his toes. Also, you can note how his hands, feet, and body react toward the direction of flight and speed - he also blends his angles (slightly buggy, but remember its work in progress). Anyway, the SDK is great with somethings, and other things its a load of blop. Though its what we are using and so we will push it to its limits and carry on kicking ass.