moving thousands of objects is very slow, Draw calls

Hi,

i try to move many planes (with a mesh renderer and a rigid body).
But my fps drop to 2-3 when all start moving.
Up to 100 objects is fine, but after that it starts to lag.

(Background: Spaceships moving from one planet to antoher).
I already pool the objects,so they are instaciated with the start of the game, so this is not the bottleneck.
Acutally i sent 900 ships but my draw calls go up to 2500!

Help is really appreciated.

there is actually a very good presentation from one of the unite conferences explaing how to do this with a boid script, its about an hour long but explains how to get 500hundred birds flying around smoothly

http://unity3d.com/unite/archive/2007

Thanks, i am batching now many objects!
This site was also helpful: http://flyclops.com/2d-in-unity-or-hobbling-a-giant-176