A man stands before a lava eruption on Holuhraun, northwest of the Dyngjujoekull glacier, in Iceland on Monday. Lava fountains gushed along a lengthy volcanic fissure near Iceland’s subglacial Bardarbunga volcano Sunday, prompting authorities to raise the aviation warning code to the highest level and close the surrounding airspace.

The warning was lowered 12 hours later as visibility improved and it was clear that no volcanic ash was detected.

An Icelandic volcano last threatened air travel in 2010, when thick volcanic ash from the erupting Eyjafjallajokull glacier drifted over Europe, emptying the skies of planes for days.