(AP) -- The drifting plume of ash from Chile's erupting volcano forced new cancelations of dozens of flights on Monday in Argentina, Uruguay and other South American countries, even as airlines in Australia began trying to move a backlog of volcano-stranded passengers.
Buenos Aires' two main airports reopened on Monday after halting flights for a day due to the cloud of fine grit, which can damage airplane engines. The civil aviation agency said the ash in the air had diminished.
The cloud also has drifted across the Pacific Ocean, and most flights between Australia and New Zealand remained grounded.
In Argentina, U.N. Secretary General Ban Ki-moon was among those inconvenienced by the closings of Buenos Aires' airports. He was forced to fly instead into the city of Cordoba and travel on by car to visit President Cristina Fernandez in the capital.
All flights were canceled at the international airport in Montevideo, Uruguay, and some were grounded in Chile, Paraguay and Brazil.
Airlines in Australia started flying a backlog of tens of thousands of stranded passengers to and from the city of Melbourne on Monday as ash cleared somewhat after forcing hundreds of cancelations. Australia's Bureau of Meteorology said the ash cloud was large enough, however, to disrupt flights later in the week.
Early Tuesday, more Australian flights were canceled because of the ash, this time out of a midsize southern airport. About two dozen flights into and out of Adelaide were canceled, though Qantas and Jetstar said they would reassess that decision later in Tuesday.
Chile's Cordon Caulle volcano began erupting on June 4. Since then, about 4,000 Chileans have been evacuated from the area.
Ash began to fall on Monday in some towns of the Rininahue Valley in Chile, where residents had been evacuated last week by troops and police. Television images showed roofs and cars coated with ash.
Army troops were handing out masks in other nearby areas as a precaution in case the ash cloud drifted toward them, said Enrique Valdivieso, the director of Chile's National Geology and Mines Service.
Last week, the ash cloud grounded hundreds of flights in parts of South America.
Aerolineas Argentinas rerouted incoming flights from Europe on Monday away from Buenos Aires and instead to Cordoba, about 430 miles (700 kilometers) to the northwest.
Other regional airports in southern Argentina have been closed since last week.
Brazilian airlines Gol and TAM informed passengers that flights to Argentina and Uruguay were called off Monday until further notice because of unsafe conditions caused by the shifting ashes.
In Chile, the airline LAN on Sunday and Monday halted some flights between Santiago and various cities in South America, as well as to Australia and New Zealand. In Colombia, Avianca suspended flights between Bogota and Buenos Aires on Sunday and Monday.
The Chilean volcano wasn't the only one causing problems for airlines and travelers. U.S. Secretary of State Hillary Rodham Clinton was also cutting short a three-nation tour of Africa due to a volcanic eruption that has created an ash cloud over parts of East Africa.
Explore further: NASA's Landsat satellite looks for a cloud-free view