[1.8] Rideable Flying Mob

Hi,

I created a flying mob which is rideable. I can mount and fly horizontal but now I want to do the vertical movement too and I can't figure out how. Basically I want the same movement as in creative. My current idea is using to keyinputevent and send a packet to the server to set the corresponding motion. But in my opinion this isn't the best solution. If anyone has another idea or knows that a good solution already exists I would really appreciate it.