Spain shut 19 northern airports including Barcelona Saturday because of the cloud of ash blowing south from a volcano in Iceland. The government said over 400 flights would be cancelled, leaving almost 40,000 people stuck in airports stretching from La Coruna in the northwest to Barcelona in the northeast. Air traffic was expected to be affected until 2 A.M. (0000 GMT) Sunday morning, at which time flights would gradually resume. However, the government said there was a chance the cloud could still be affecting Spain next week. “We don't rule it out and we will make alternative plans,” Transport Minister Jose Blanco told a news conference. He said extra places had been made available on long-distance trains, and extra buses and boats were being laid on to help people reach their destinations. Many flights between Europe and North America were either delayed or canceled Saturday due to the spreading cloud of volcanic ash stretching across much of the northern Atlantic, the European flight control agency said. Flights had to be rerouted north over Greenland or south over Spain to avoid the 1,200-miles-long cloud stretching from Iceland to northern Spain, Eurocontrol said. This will increase flying times by about an hour in either direction. “We assume that basically most of the trans-Atlantic flights will have to be rerouted on Saturday,” Eurocontrol spokeswoman Kyla Evans said. “We expect substantial delays because of that.” Approximately 600 airliners make the oceanic crossing every day. Around 40 percent will be rerouted southward and the rest will skirt Iceland from the north. The European air traffic agency Eurocontrol warned on Saturday of a rise in emissions from the volcano, Eyjafjallajokull.