US airlines have cancelled flights in and out of Mexico City's airport for a second day as a precautionary measure as the nearby Popocatepetl volcano continued to emit vapour and ash.
More than 600 passengers remained stranded in the airport of the Mexican capital after Alaska Airlines, United, Delta and AirTran cancelled about a dozen flights on Friday.
No ash has fallen at the airport, Jorge Gomez, spokesman for Mexico City airport, said, though dust particles have been detected from the volcano that is about 65km away.
On Thursday, at least six US airlines cancelled more than 40 flights as the volcano spewed a 1.5 kilometre-high plume of ash that drifted over large parts of Mexico City. The volcano also spewed a hot shower of glowing rock around its crater.
"They can't even give us chairs," Mexican traveller Gabriela Garcia said as she stood in a long line at a Delta counter with some 200 other people. "Nobody knows anything, nobody says anything. We've been standing for six hours."
Another Mexican traveller, Eusebio Pacheco, said that he had also been waiting in line for six hours with his wife, hoping to finally take off to the Canadian province of Quebec.
"We don't know anything, they don't tell us anything, we're desperate," he said, adding that two flights were cancelled. They hoped to fly out on Saturday.
Mexico's National Centre for Disaster Prevention reported that there had been 99 tremors and exhalations of medium and high frequency from the volcano on Friday afternoon.