Looks like your to far away from the surface and the paint is drying before it hits the model.
What type of airbrush are you using? Some of the expensive double actions have fine to very fine needles which work great at close range however large area coverage is more diffucult.
Try lowering or increasing your air pressure if you have the capabilities, to low of pressure won't "move" alot of paint, but high pressure may cause the paint to "bounce" on the surface.
Make sure your paint is thinned correctly, this is a point of discussion among many, the beginners rule is the consistency of 2% milk. When you drag a drop of paint up the side of your mixing cup it should run down but leave pigment behind. Also try to use the recommended thinner for the brand and type of paint your using.
Most IMPORTANTLY practice, practice, practice. Experiment with different settings of above mentioned variables and it will work out. PRACTICE, PRACTICE, PRACTICE.
Good luck, let us know your progress and HAPPY MODELLING.