Eruption activity was at a maximum in the first hour, and by the first night the fissure on Hekla had opened to a length of 6-7 km. The steam column rose to a height of almost 15 km, and ash was transported to Grímsey. During this eruption, a NASA DC-8 aeroplane accidentally flew through the plume with all instruments switched on, resulting in unprecedented measurement of a young volcanic plume.