The problem with airplanes in OFP is that they do not like to point their nose down very steeply if the AI is in control. If you force them to have increased downward velocity using a script, the AI tries to fight againt it so the plane will be dropping in altitude, but the AI is trying to not dive so he is pointing the nose up, so it looks really stupid. The only way to do it might be to remove the AI pilot, then inflict the needed velocity vecotros on the empty plane, then put the AI back in the plane as soon as the nose is pointed sufficiently downward. The AI should then pull out of the dive on his own. This actually sounds like it could be a fun little scripting exercise, so if you can tell me where to download the Stuka addon you are using I will try to make a dive script for it. In the mean time I can experiment with the BIS A10.