Iceland Volcano
http://www.pdc.org/PDCNewsWebArticles/2010/Iceland/eruption.htm
1. The plate tectonics could have caused a small earthquake and shook the volcano causing it to erupt.
2. Because it is all ash and you can't fly a plane through the ash. It messes up the engine.
3. The air is all polluted and ashy.
4. Because of the distance between the effected area, and the united states is far.