LONDON --Thick drifts of volcanic ash blanketed parts of rural Iceland on Friday as a vast, invisible plume of grit drifted over Europe, emptying the skies of planes and sending hundreds of thousands in search of a hotel room, a train ticket or a rental car. Polish officials worried that the ash cloud could threaten the arrival of world leaders for Sunday's state funeral for President Lech Kaczynski and his wife Maria in the southern city of Krakow. So far, President Barack Obama, Russian President Dmitry Medvedev and German Chancellor Angela Merkel are among those coming and no one has canceled. Kaczynski's family insisted Friday they wanted the funeral to go forward as planned but there was no denying the ash cloud was moving south and east. The air traffic agency Eurocontrol said almost two-thirds of Europe's flights were canceled Friday, as air space remained largely closed in Britain and across large chunks of north and central Europe. "The skies are totally empty over northern Europe," said Brian Flynn, deputy head of Eurocontrol, adding "there will be some significant disruption of European air traffic tomorrow." The agency said about 16,000 of Europe's usual 28,000 daily flights were canceled Friday twice as many as were canceled a day earlier. Only about 120 trans-Atlantic flights reached European airports compared to 300 on a normal day, and about 60 flights between Asia and Europe were canceled.