Because if Askja volcano quick inflation, that is now currently at 7 cm, Department of Civil Protection and Emergency Management has declared uncertain level and yellow alert for flight.
Inflation is quick in Askja volcano and is now at 7 cm. When or if that is going to result in an eruption is impossible to know. Current Askja volcano is what remains of a mountain that blew up in an large eruption in the year 1875 century. Most eruptions are just lava flows, unless they happen to start in a water, then explosive activity happens while water remains.