This paper presents some observation results of the attachment test of a wind turbine blade as described in the upgrade of the IEC-61400-24. The optical observations were performed by means of high-speed video and UV-sensitive photo camera. This study investigates the effects on the leaders emerging from the blade comparing three different air-terminals: discrete receptors, discrete receptors with diverter strips and metallic tip. In the first two types, salt mist pollution was applied to the blade. For non polluted tips positive leaders appeared from receptors towards the ground avoiding the blade surface. When the blade was polluted additional leaders emerged moving horizontally. Moreover, in this situation the leader progressed on the blade surface. Pollution also produced the inception of more leaders when the blade was equipped with discrete receptors and diverter strips.