Do you see it? The plane was making an awful loud sound....getting your attention I suppose! This was in Algarve area in southern Portugal, summer 2007.
Seeing the wings are on the bottom of the fusselage, i am thinking that this is not a usual towing plane for adverticement, they usualy have their wings on the top of the fusselage, to have more and better sight to the field where they need to pick up the banner. My guess is that this is a crop spray plane, they do have a bigger engine and might explain the loud noice ?