PORT-AU-PRINCE, Haiti  When Air Force special operations controllers stepped off a transport plane Wednesday night at Haiti 's main airport, they found chaos.

One day after the earthquake in Haiti struck, relief planes were coming in from all directions, landing on a first-come-first-served basis and getting too close to one another on the ground. Nobody was coordinating. Aid wasn't moving.

The air-traffic control tower was damaged and unsafe. So Sgt. Chris Grove, whose expertise extends to calling in airstrikes from the ground in Iraq and Afghanistan, brought his squad to a spot near the runway and set up what would become an air-traffic control center. They went to talk to pilots on the ground. "We told them, hey, we're Air Force combat controllers. We're taking over the airfield," Grove said. From a dirt patch, two young American sergeants began directing air traffic for one of the largest humanitarian operations in history.

It was the beginning of an operation that, by Sunday, had unclogged one bottleneck preventing aid from reaching Haiti's desperate population. It was no magic bullet — relief officials searched for helicopter landing zones and overland routes through which to bring in aid.

By Sunday, the Air Force had landed some 300 planes, most of them laden with relief supplies. Four large forklifts unloaded the pallets as they landed and the aid was shipped out on trucks and helicopters. Incoming planes were required to file flight plans with landing times to ensure an orderly flow. The Haitian government has signed an agreement granting the U.S. formal control of the airport.

"This is a herculean effort out here," said Col. Ben McMullen, who like virtually all American troops on the ground here is working 16 hours a day, sleeping on a cot and eating meals out of a plastic pouch. "It feels great; it really does. That's what we're here for, is to land airplanes."

More than 2,000 U.S. citizens have been evacuated, leaving "on every available aircraft," Air Force Col. Buck Elton said Sunday.

It didn't always go smoothly. With only one forklift at first, the Air Force couldn't quickly unload the planes coming in Thursday and Friday, McMullen said. Because of that, and because the airport lacked ground refueling, many planes were turned away. Some nations and aid groups did not initially cooperate with the U.S. military, McMullen said.

The Geneva-based aid group Doctors Without Borders said the bottleneck at the airport was "a major difficulty." It said a flight carrying its own inflatable hospital was denied landing clearance and was being trucked overland from Santo Domingo, delaying its arrival by 24 hours.

"I know we got some bad publicity about turning some away, but there was nothing we could do," Grove said, standing on the airfield between landings. "Our job is to run a safe and effective air-traffic control operation."

On Sunday, all manner of aircraft, including a Chinese 747 jumbo jet, were lined up along the airfield. Forklifts were unloading the pallets into convoys of trucks. The drone of jet engines and helicopter rotors was constant.

When they first arrived, the Air Force special operators set up a headquarters in a rat-infested, trash-strewn hangar. Now cleaned up, that has become the central military headquarters for the relief effort. It's where Secretary of State Hillary Rodham Clinton met Haitian President René Préval on Saturday.

Contributing: The Associated Press