The red warning code — the highest in the country’s alert system — meant that no flights are allowed in an airspace area of about 40 square nautical miles north of the eruption area, up to 6,000 feet from the ground. Aviation officials said the restrictions do not affect commercial flights, which fly much higher than that.
No volcanic ash has been detected, and the Civil Protection Department said all Icelandic airports remained open.
The fissure eruption was a crack that came to the surface about 40 km from the main Bardarbunga volcano, which lies under the vast Vatnajokull glacier that dominates the eastern corner of Iceland.