GIMP has a very powerfull brush tool. It is already far far
better than most of the expensive rivals. 

Brush file formats native to the GIMP are GIH, GPB and GBR. 
Brush files must be placed in your ~/.gimp_verison/brushes directory 
to be available for your use in the Brush Selection dialog. 

Use Refresh in Brush Selection Dialog to see the new brush(es) 
without restarting GIMP.

Gimp Airplane Brush Contains a B&W airplane with angular setting.

Freely distributable.

Happy Gimping...
Nevit Dilmen
http://start.at/nevit