Flights in the United States and Europe are being disrupted by clouds of ash spewing from a volcano in Iceland.
The volcano's smoke and ash poses a threat to aircraft because it can affect visibility, and microscopic debris can get sucked into airplane engines and can cause them to shut down.
"Come on. Volcano in Iceland? There's only ice in Iceland," said Bharti Panjwani, delayed O'Hare traveler.
"The problem is that nobody knows anything. We know that flights north of Europe are cancelled. Ours is delayed," said Piotr Grekowicz, another delayed passenger.
Flights worldwide are grounded because the ash cloud has drifted over parts of Europe reaching 55,000 feet.
""If it's ingested into an engine, it can affect the performance and ultimately cause the engine to shut down," said Paul Haskins, Air Traffic Control Service.
O'Hare aviation officials say 20 flights are cancelled.
The Panjwanis were on their way to a wedding in India via Germany. "We were not in the airplane when this thing happened. Thank God," said Sri Panjwani.
"Nobody got upset. Nobody said, 'ah.' They just said, 'what are you going to do? It's a volcano. It's going off,'" said Lynne Sootheran whose flight was diverted to O'Hare.
"I would have rather turned around than to have flown through the ash," said Kent Simmonds who arrived at O'Hare on a diverted flight.
While some of the flights were delayed a few hours, others are cancelled altogether. And some of those passengers aren't able to rebook their trips until the middle of next week.
"More time for vacation," said Ola Mogstad, traveler.
Even if it's at O'Hare Airport.
The Associated Press contributed to this report.