PERMISSION for planes to fly through the volcanic ash cloud hovering above Europe has been granted – but it may not be completely safe just yet, according to the University of Hertfordshire.

The Hatfield-based institute is measuring the current levels of volcanic ash over the UK, which led to British airspace being closed for six days before re opening last night (Tuesday).

In partnership with the University of Reading, scientists have developed a unique probe attached to a meteorological balloon, which was originally designed to measure dust storms in the Sahara desert.

But following the eruption of a volcano in Iceland, the probes are now being used to check the dust levels in the sky.

Three probes are now being launched in stages from Scotland to support Met Office findings.

Dr Joseph Ulanowski, of the University of Hertfordshire’s Science and Technology Research Institute, said: “We launched the first one on April 19 and found a four kilometre high, 600-metre thick layer of dust which was in keeping with Met Office findings.” “Volcanic ash is much like a desert storm and we estimated that a typical jet engine would ingest some 60 billion of these highly abrasive dust particles every second.”

According to Dr Ulanowski, aircrafts have zero tolerance to volcanic ash, and the only safe approach would be to open up air corridors in areas where there is no dust in the atmosphere.

“We expect temporary gaps in the dust, and for it to be episodic until the weather changes,” Dr Ulanowski said.

“In the meantime, we will use our probes sparingly so that we can endorse Met Office models.”