The Model Air range of acrylics are specially formulated by Vallejo for spraying by airbrush. With finer milled pigments and a higher adhesion acrylic resin, they cause less clogging of the airbrush and stick to a wide range of surfaces, especially hard plastic as used in many kits and white metal.
The range is aimed primarily at model-makers working on modern armour and aircraft models, with a great range of camouflage shades, but there are some lovely metallics and primary colours for airbrush work on a wide variety of models.
Model Air paints can be used neat from the bottle, or diluted with water or Vallejo airbrush thinner. The thinner is the best option if you tend to dilute significantly; water works well up to a point, but beyond that point the acrylic resin gets diluted to a level where adhesion is reduced.