Four bases used by U.S. aircraft - two in England and two in Germany, including Ramstein - have been closed down, forcing planes to fly southern routes, but the Pentagon says that to date there has been "no major impact" on operations.
Volcanic ash sifted down on parts of northern Europe on Friday and thousands of planes stayed on the tarmac to avoid the hazardous cloud. Travel chaos engulfed major European cities and the U.N. warned of possible health risks from falling ash.
Eurocontrol, the European air traffic agency, said the travel disruptions that reverberated throughout the world Thursday were even worse on Friday, with about 11,000 flights expected to operate in Europe instead of the usual 28,000. It said delays will continue well into Saturday as the massive yet invisible ash cloud moves slowly south and east.
"There will be significant disruption of air traffic tomorrow," spokesman Brian Flynn said, adding the agency would hold a meeting Monday of aviation officials from all 40 Eurocontrol countries.
Train stations, hotels and car rental agencies were jammed in key European cities by people scrambling to make alternative plans. Extra long-distance trains were put on in Amsterdam and lines to buy train tickets were so long the train company was handing out free coffee.
The high-speed Thalys trains, a joint venture of the French, Belgian and German rail companies, allowed passengers to buy tickets even if there were not enough seats.
Aviation experts said it was among the worst disruptions Europe has ever seen.
Ice chunks the size of houses tumbled down from a volcano beneath Iceland's Eyjafjallajokull glacier on Thursday as hot gases melted the ice. The volcano began erupting Wednesday for the second time in less than a month.
As torrents of water roared down the steep slopes of the volcano, flash floods washed away chunks of Iceland's main ring road. More floods are expected as long as the volcano keeps erupting, which scientists said it was continuing to do in daily pulses.
The cloud of basalt, drifting between 20,000 to 30,000 feet high and invisible from the ground, at first blocked the main air flight path between the U.S. east coast and Europe. On Friday, the British Meteorological Office said the cloud's trajectory was taking it over northern France and Austria and into eastern and central Russia at about 25 mph.
Fearing that microscopic particles of highly abrasive ash could endanger passengers by, authorities shut down air space over Britain, Ireland, France, Denmark, Norway, Sweden, Finland and Belgium. That halted flights at Europe's two busiest airports - Heathrow in London and Charles de Gaulle airport in Paris - as well as dozens of other airports, 25 in France alone.
Only about 120 trans-Atlantic flights reached European airports Friday morning, compared to 300 on a normal day, said Eurocontrol. About 60 flights between Asia and Europe were canceled.
U.S.-based airlines cancelled more than 205 transatlantic flights on Thursday alone, reports CBS News Correspondent Elizabeth Palmer from London.