MOUNT MERAPI, Indonesia -- Indonesia's most volatile volcano sparked transportation chaos Sunday, with several international airlines canceling flights to the capital and neighboring Malaysia airlifting out hundreds of its citizens.
Panicked residents who live near the base of Mount Merapi -- which has claimed 138 lives in two weeks -- crammed into trains and buses to seek temporary refuge with family and friends elsewhere.
The notoriously unpredictable volcano unleashed its most powerful eruption in a century Friday, sending hot clouds of gas, rocks and debris avalanching down its slopes at highway speeds, torching houses and trees and leaving a trail of charred corpses in its path.
A mass burial for some of the 90 who died in that blast was planned for later Sunday.
Merapi, meanwhile, showed no signs of tiring, sending out thunderous claps as it shot ash up to four miles (six kilometers) into the air, dusting windshields and rooftops hundreds of miles away.
Just days before President Barack Obama's planned trip to Indonesia -- his second stop in a 10-day Asian tour -- several international airlines canceled flights to Jakarta, 280 miles (450 kilometers) to the west, due to the risks posed by volcanic ash.
It can clog engines and harm other parts of the aircraft.
Paul Belmont, a U.S. Embassy spokesman, said there was no talk yet of changing Obama's schedule.
"But certainly, if the situation evolves into something like what we saw in Europe not long ago (when the eruption of Iceland's Eyjafjallajokul closed airports for a week) it's something we'd have to take seriously," he told The Associated Press on Sunday.
Almost all international flights in and out of Jakarta were canceled Saturday. While some airlines slowly started resuming operations Sunday, Lufthansa, EVA Air, Philippine Air and others were still on the ground.
The Royal Malaysian Air Force, meanwhile, was sending three C-130 transport planes to the city of Solo, 20 miles (30 kilometers) from the volcano, to pick up 664 citizens, many of them university students.
The first batch returned home Sunday evening and the rest were scheduled to head out early Monday.
Merapi's latest round of eruptions began Oct. 26, followed by more than a dozen other powerful blasts and thousands of tremors. More than 200,000 people -- many of whom normally live on the fertile slopes of the volcano -- have since jammed into emergency shelters.
With muddy floors and flies landing on the faces of sleeping refugees, many complained of poor sanitation, saying there were not enough toilets or clean drinking water.
The Indonesian government has put Yogyakarta, a city of 400,000 people 20 miles (30 kilometers) from Merapi, on high alert.
Though there have been no orders to evacuate, bus and train stations were crammed with people planning to stay with family and friends far away until things returned to normal.
"My parents have been calling since Friday saying 'You have to get out of there! You have to come home!" said Linda Ervana, a 21-year-old history student who was waiting in a train station with three other friends from her Yogyakarta university.
After failing to get tickets, they finally decided Sunday to rent a minibus with some other classmates.
"It feels like that movie '2012,"' said Ervana's 22-year-old friend, Paulina Setin. "Like a disaster in a movie."
Others in Yogyakarta hopped onto motorbikes and into cars with their families, saying the volcanic ash was making it hard to breathe.
"What choice do we have?" asked Sukirno, 37, as he sped away with his wife and their 8-year-old daughter, saying he worried about the effect on their health.
"We were thinking about going to one of the refugee camps, but it's better all around if we stay with relatives."
The biggest threat to Yogyakarta, experts say, are not searing gas clouds, but the Code River, which flows right into the city's heart from the 9,700-foot (3,000-meter) mountain.
It could act as conduit for deadly volcanic mudflows that form in heavy rains.
Racing at speeds of 60 mph (100 kph), the molten lava, rocks and other debris can destroy everything in their path. People living near the river's banks have been advised to stay away.
Indonesia, a vast archipelago of 235 million people, is prone to earthquakes and volcanoes because it sits along the Pacific "Ring of Fire," a horseshoe-shaped string of faults that lines the Pacific Ocean.