A volcanic eruption in Iceland has made air travel to northern and western Europe mostly inaccessible. It is not safe to fly planes through the cloud of volcanic ash, as the ash clogs the airplane's air intake and fouls the engine.
So, if you really wanted to go there, how would you do it?
You could, as an immediate alternative, fly to southern Europe, and take trains to your final destination. Europe is quite interconnected with trains, even going to the UK, an island, via a tunnel.
But let's say you really really needed to fly directly to, say, Finland, and you lose a billion dollars for every moment after 8 hours from now. How could you fly directly?
You'd have to modify the plane. It would have to accept air not directly, but through a series of filters. It would need thick and tough hulls and windows. Or, alternatively, instead of gasoline it would have a non-breathing nuclear reactor. The filters would be in layers, and would have to be changed in mid-flight.
And when the plane landed, it would need to be instantly stripped for maintence. Flying through the ash and debris would have eroded every surface on the outside, and many clogged filters would need to be thrown away.
But it would be possible. And if you needed it that badly, you could do it.