I would only make 1 suggestion at this point for flying:
Have the mouse control the camera, not the cursor. Have the javelins turn a maximum rate towards the direction camera is facing until the javelin is centred. Having to constantly reposition the mouse on the mouse pad because it keeps readjusting the position towards the centre just doesn't work well. In the short term it's pretty annoying and long term will become a frustration.
Either implement something like the above or have the option to not have the game keep centering the mouse would be nice. A controller can keep a joystick held hard in one direction to make a turn without having to constantly reposition the stick - mouse control needs the same ability.