The volcanic eruption in Iceland has stopped all air traffic into and out of Europe. It’s become such a disaster that thousands and thousands of people are stranded in airports everywhere. Asian flights to Europe are canceled, US flights entering Europe are also canceled (unless you want to go to Reyjavik which ironically is open).
It is amazing how tiny ashes can stop aircrafts weighting tons. The Guardian has an article on why volcanic ashes are dangerous. And I collected a set of beautiful volcanic eruption photos from both amateurs and professionals.
If you are stuck and need flight information, check the NY Times flight sheet for details.
It will be at least a week before any airport returns to normalcy. I read an article that said 200million dollars is lost each day because of the delays.