A study on ash blasted from volcanoes is a first step towards accurately assessing where it is safe to fly during eruptions, according to the authors. The researchers found that the ash grains ejected into the atmosphere have diverse shapes and properties. They also learned that big grains can travel further than was previously estimated. All this could improve existing models of ash concentrations, which governments and airlines use to make flight decisions during eruptions, they say. Ash can cause aircraft engines to fail.