Volcanic eruption causes more than 40 U.S. flights in and out of Mexico to be grounded Six U.S. airlines including Delta and United have canceled 47 flights as a precaution Otherwise the airports in Mexico City and Toluca are operating as normal Popocatepetl volcano has spewed out ash, steam and glowing rocks but none has reached the airports At least six U.S. airlines canceled more than 40 flights into and out of Mexico City and Toluca airports on Thursday after the Popocatepetl volcano spewed out ash, steam and glowing rocks, airport officials said. Mexico City airport spokesman Jorge Gomez said U.S. Airways, Delta, United, American and Alaska Airlines canceled 47 flights as a precaution. But he said the airport otherwise continues to operate normally and that by Thursday afternoon no ash had reached the area, about 40 miles (70 kilometers) from the volcano. Mexico's Popocatepetl volcano, some 55 km from Mexico City, has spewed out ash, steam and glowing rocks Stranded passengers look at a flight departure board after their flight was cancelled at the Benito Juarez international airport in Mexico City July 4 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 canceled flights from Dallas and Fort Lauderdale, said spokesman Alejandro Munoz. The airport, about 35 miles (60 kilometers) from Mexico City, also continued to operate normally, Munoz said. Authorities registered several tremors Thursday at the 17,886-foot (5,450-meter) volcano, which has been spraying a fountain of hot rock and ash for the last 24 hours. Six carriers including U.S. Airways, Delta, United, American and Alaska Airlines have canceled 47 flights as a precaution Federal civil protection authorities established a 7-mile (12-kilometer) safety radius around the Popocatepetl, which means no one can enter that area. They also are ensuring that no cars transit through the Paseo de Cortes, a mountain pass between the Popocatepetl and Ixtaccihuatl volcanoes. An iconic backdrop to Mexico City's skyline on clear days, Popocatepetl sits roughly halfway between Mexico City and the city of Puebla. A stranded passenger talks on his mobile phone after his flight was cancelled at the Benito Juarez international airport in Mexico City An iconic backdrop to Mexico City's skyline on clear days, Popocatepetl sits roughly halfway between Mexico City and the city of Puebla