Beware of Eyjafjallajokull: Airports across Europe canceled all flights on Saturday as the cloud of ash from the Icelandic volcano wreaks havoc with air traffic. From Russia to Britain, about 16,000 flights are expected to be grounded Saturday and nothing will fly in or out of cities like London, Paris, and Berlin until Sunday. Though the cloud does not actually pose any problems to visibility, the danger comes from the tiny particles of rock, glass, and sand that make up the ash—experts say they can lead to electrical and engine failure. "I cannot say whether it's an overreaction or underreaction," one air travel official told CNN. "I think everybody is working in the interest of safety." With the cloud drifting east, there is no telling how long the disruption could continue.