Myanmar's isolationist ruling junta is now allowing U.S. military cargo planes to regularly fly relief supplies into their largest city to provide aid to cyclone survivors.
But if the aid is to get out to the estimated 2 million people who need it most, Myanmar is going to have to make another big concession: letting the U.S. start flying helicopters directly into the hardest-hit areas and allowing boots on the ground.
So far, that is where the junta draws the line.
Myanmar, whose ruling military generals are intensely sensitive to what they see as outside meddling, has limited the U.S. military to the Yangon airport, where emergency supplies must be unloaded by hand.
Once the planes are unloaded, they are quickly sent back to their makeshift base in Utapao, in central Thailand east of Bangkok.
The U.S. military has flown 13 C-130 cargo planes loaded with 156.6 tons of aid into Yangon over the past four days. Five flights flew on Thursday, military officials said, and another eight were expected to take off Friday.
The C-130s have brought in much-needed supplies including water, mosquito nets, blankets, plastic sheets and hygiene kits. But aid groups say the airport soon will have more supplies than it will be able to handle, meaning bottlenecks and delays.
The U.S., which was conducting its annual Cobra Gold military exercises in the area when the cyclone hit, has 11,000 troops and a flotilla of ships ready to go. U.S. military assets from as far away as Guam and Japan are in Thailand or off its waters.
"We've got a lot of assets in the field," said Lt. Col. Douglas Powell, a Marine spokesman for the relief effort, called Operation Caring Response. "We're not limited to our C-130s."
Largely with the use of helicopters, which have tremendous versatility, the U.S. military made a major contribution to the international relief effort after the catastrophic 2004 tsunami killed more than 230,000 people in a dozen nations around the Indian Ocean.
Helicopters to the devastated Irrawaddy Delta and some troops on the ground would be an essential part of a stepped-up relief effort in Myanmar as well.
To prepare for such an operation, the U.S. is moving several ships that can support helicopters into international waters closer to Myanmar and has scouted out possible staging sights on land, including Mae Sot, a Thai border town with an air base about 250 miles from the disaster zone.
Pentagon spokesman Bryan Whitman said Thursday that Navy ships from the USS Essex expeditionary strike group were moved slightly after Wednesday's warning of another approaching storm, but they are now some 30 miles off Myanmar's coast, also waiting to help, if asked.
"The need is still high," Whitman said.
Thailand also has sent military flights to Yangon. The British, French and Australian militaries have diverted assets to help, but are still awaiting approval from the Myanmar leaders to actually go in.