What volcano erupted in 2010 that caused the largest air-traffic shut down since World War 2?

The volcano that erupted in 2010, causing the largest air traffic shutdown since World War II, was Eyjafjallajökull in Iceland. Its eruption produced a significant ash cloud that spread across Europe, leading to widespread flight cancellations and disruptions affecting millions of travelers. The ash posed a serious risk to aircraft engines, prompting authorities to close airspace over many countries.