At least six US airlines cancelled 47 flights to and from Mexico City and Toluca airports after the Popocatepetl volcano spewed ash, steam and glowing rocks.
Mexico City airport spokesman Jorge Gomez said US Airways, Delta, United, American and Alaska Airlines axed the flights as a precaution. But he said the airport otherwise continued to operate normally and that by last night no ash had reached the area, about 40 miles north west of the volcano.
Mr Gomez said that among the routes affected by the cancellations were flights to Houston, Dallas, Denver, Phoenix, Chicago and Los Angeles.
At nearby Toluca airport, Spirit Airlines cancelled flights from Dallas and Fort Lauderdale, said spokesman Alejandro Munoz. The airport, about 35 miles from Mexico City, also continued to operate normally, Mr Munoz said.
While there was no volcanic ash falling near the Mexico City airport, people in the capital's southern neighbourhoods reported seeing a light coating on their cars and homes.
Mexico City civil protection secretary Fausto Lugo said the main risk for the metropolis was people not knowing how to handle ash and how to protect potable water from becoming contaminated.
"If there is an eruption, we wouldn't evacuate Mexico City," Mr Lugo said. "For us the main risk is the handling of volcanic ashes."
Authorities registered several tremors yesterday at the 17,886ft volcano, which has been spraying a fountain of hot rock and ash for the last 24 hours.
Federal civil protection authorities established a seven-mile no-go area around the Popocatepetl. They also are ensuring that no cars travel through the Paseo de Cortes, a mountain pass between the Popocatepetl and Iztaccihuatl volcanoes.
Popocatepetl an iconic backdrop to Mexico City's skyline on clear days, sits about halfway between Mexico City and the city of Puebla.