A huge cloud of volcanic ash from Iceland has disrupted air travel across Europe for a second day, as stranded passengers face the most extensive shutdown of airspace since the September 11, 2001 terrorist attacks. The European air traffic conrol agency, Eurocontrol, said about 17,000 flights are likely to be canceled Friday and authorities say the disruptions will continue into Saturday. Officials say about half of the daily flights between Europe and North America would be cancelled Friday. Many flights between Asia and Europe were also affected. It is not clear how the ash cloud will affect the arrival of world leaders planning to attend the state funeral Sunday of Polish President Lech Kaczynski. The funeral is to be held in Krakow, in southeastern Poland. Polish officials have closed the airspace in the northern part of the country. Major European airports were shut down Thursday, leaving tens of thousands of passengers from the United States, Europe, and Asia stranded. Several northern European countries - including Britain, Norway, Sweden, and Denmark - had completely closed their airspace. Wednesday's eruption in southeastern Iceland melted part of a huge glacier, causing floods that forced hundreds of residents to flee their homes. The volcano sent ash and debris about eight kilometers into the sky. In addition to reducing visibility, aviation authorities say volcanic ash contains small particles of glass that can cause jet engines to shut down in midflight. They say airplanes struck by volcanic debris have in some cases plummeted thousands of meters before pilots were able to restart the engines. The Icelandic volcano has erupted twice since March 20. It had been dormant for nearly 200 years. Geologists say volcanoes are notoriously unpredictable.