Given a reference text that describes the air travel disruption after the 2010 Eyjafjallajökull eruption, how long was the air travel over Europe disrupted for?

Initially there was an uninterrupted shutdown of the air travel from April 15 until April 23. There were intermittent disruptions in different parts of Europe in the following weeks until May 17. Overall, the air travel over Europe disrupted for 33 days between April 15 and May 17 2010.