Buffeted by swirling winds, the helicopter slid crabwise as the pilot struggled to land on a tiny sloping field hacked from the side of a steep mountain. He got it right on the second try and earthquake survivors rushed the bulky craft, shoving aboard the injured and the merely desperate as soldiers on the ground tried to control the crowd.

Minutes later, the Pakistani army helicopter lifted off and returned to its temporary base, passing mile after mile of shattered ridge-top settlements where villagers waited for help like shipwreck survivors stranded on atolls.

Nine days after a massive quake rocked northeastern Pakistan, countless villages and settlements remain cut off by landslides, posing a nightmarish challenge for relief workers racing to evacuate the injured -- many of whom have yet to receive any medical attention -- and provide food and shelter to those remaining behind. Authorities estimated the death toll in Pakistan at 40,000, but warned that the number could rise sharply as more bodies are found beneath the rubble.

With winter fast approaching, aid workers and Pakistani army troops were sprinting to reach survivors any way they could -- on foot, by mule train and especially by helicopter, threading their way through mountain slots and steep-walled valleys on difficult and dangerous airlift missions that have already claimed seven lives.

Such is the desperation of earthquake survivors that the army no longer lands helicopters in cut-off villages without first deploying troops to ensure that crowds do not surround the aircraft and cause an accident, according to the pilot on Monday's mission.

"They're rushing the helicopters. They're trying to topple it over," said Maj. Rehan Abdul Hafeez over the intercom of the Soviet-made Mi-17 transport helicopter as it chugged noisily 40 miles up the Kaghan Valley toward the snow-capped Karakoram range. "It's now the 10th day. They're more sick. They're hungry. And they're more cold."

The Oct. 8 earthquake was the worst natural disaster in Pakistan's history, smashing towns and villages across a broad mountainous swath of Pakistani-controlled Kashmir and the adjacent North-West Frontier province. Besides those killed in Pakistan, the 7.6-magnitude temblor is thought to have killed about 1,350 people in the part of Kashmir that India controls. U.N. officials estimate that 2 million people were made homeless by the quake.

But the relief effort has been greatly complicated by the inhospitable terrain. Many badly damaged areas are situated in the upper reaches of remote valleys that can no longer be accessed by road. As a result, thousands of earthquake survivors are still sleeping in the open air for lack of tents or plastic sheeting, while wounds are turning gangrenous for lack of treatment, aid officials say.

"There's a lot of people sprinkled all over these mountains," UNICEF health officer Tamur Mueenuddin said on Monday at a newly established heliport in the North-West Frontier province town of Mansehra, about 50 miles north of Islamabad, the capital. "They are completely isolated. They are wounded. And there's really no way to get up there right now."

To augment Pakistan's limited fleet of helicopters, the United States is providing the relief operation with 17 choppers, some borrowed from military operations in Afghanistan, and the Bush administration has promised that more are on the way. Bad weather grounded most relief flights over the weekend, although clearing skies permitted the resumption of operations on Monday.

The hazards inherent in the missions were underscored by the crash Saturday of a Pakistani army helicopter in which all six crew members died; a day later, a Pakistani aid worker was killed by a whirring tail rotor while trying to retrieve medicine seized from a helicopter by a mob of survivors at a remote village, according to Hafeez, the pilot on Monday's mission.

Taking off from the packed-earth sports field that serves as the heliport in Mansehra, Hafeez and his co-pilot, Maj. Syed Azhar Ali, flew north with a load of UNICEF supplies and several passengers, passing first over the town of Balakot, much of which appeared to have crumbled and slid to the bottom of a hill.

"From Balakot now there's no road," said Hafeez, 35, an easygoing man in an olive-drab flight suit and baseball cap. "It's all blocked."

The helicopter flew above the turbulent Kunhar River, swinging low over flat ridge tops. As livestock scattered in panic, the aircraft hovered above terraced fields of yellowing corn while crew members shoved out supplies, targeting perhaps a half-dozen settlements along a 10-mile stretch.

"Wherever we see there are tents, we drop food," said Ali, the co-pilot. "And wherever we see no tents, we drop tents and food."

The trickiest part of the mission came when the pilots battled crosswinds to land in the village of Jared, where a hundred or more people -- some of them injured -- waited near mangled tin-roofed buildings at the edge of the makeshift helipad.

First aboard were Ajib Khan, a laborer with close-cropped hair and a haunted look, and his 7-year-old daughter, Amna, whose head and limbs flopped unnaturally as he held her in his arms. She had been trapped under debris for two hours and might have broken her neck, Khan said after the aircraft landed back in Mansehra.

Other injured victims were hauled to the helicopter in blankets. A man in a woolen cap and sweater climbed in with a small boy. The child was filthy and the side of his head was covered in sticking plaster. There was a woman with two tiny infants wrapped in blankets, accompanied by an elderly man.

With other survivors struggling to force their way on board, soldiers tried to control the crowd by shoving with sticks, and in the end some villagers were turned away, including several who appeared to be injured. One of those who tried and failed to make it aboard was a bearded man who held the limp form of a woman against his shoulder.

He watched the helicopter depart with a look of anguish.

Soldiers unload supplies from a U.S. Navy helicopter for earthquake victims in northern Pakistan. The United States has provided 17 helicopters for aid efforts.