Heavy rains this week forced the cancellation of nearly all helicopter aid flights, leaving millions of desperate, drenched survivors of last week's earthquake waiting in the mountains and hills in Kashmir and in the northern Pakistani areas of Hazara and Swat. Much of the relief aid only trickled into the most needy areas, where relief supplies mean the difference between life and death in the freezing temperatures. The cancellations forced aid workers to look for donkeys and mules to get them through to the earthquake's victims. In Muzaffarabad, capital city of the Pakistani-administrated area of Kashmir, where earthquake casualties number 40,000, only two helicopters braved the foul weather that brought new misery to the area's three million homeless. The helicopter flight cancellations came a day after the first accident in the massive aid operation. Six Pakistani military personnel died when their chopper crashed near the hilly Pakistani area of Bagh. The only helicopters to fly into Muzaffarabad on Monday were German military helicopters carrying engineers to repair a remote road for use in evacuating the injured. Heavy cloud cover prevented mass evacuation of the injured by air. "There was no time to spare because thousands were at risk of death unless they got help - particularly tents, warm clothing and food," according to one military officer in charge of Muzaffarabad. He described the relief efforts as a "logistical nightmare." Presently, four countries have sent helicopters for relief work: the United States, Germany, Japan and one helicopter from Afghanistan. According to Pakistani helicopter pilots in the makeshift base camp in Balkot, it was impossible to land in some areas where there were many injured people, forcing them to deliver their supplies and take off again, despite the pleadings of people holding up the injured below. Others have made perilous touchdowns amid the piles of wreckage to haul victims aboard and ferry them to hospitals in Islamabad, Peshawar, and other major cities in Pakistan. The few people with houses that survived the earthquake have refused to go inside, fearing that aftershocks would bring down the weakened structures. At present, there are 70 helicopters conducting search-and-rescue operations in the affected areas. The flights attempted to cover the most inaccessible areas. Cargo planes carrying relief supplies from across Pakistan and across the world have filled Islamabad International Airport in Pakistan. But, for now at least, the supplies remain on the tarmac, awaiting the resumption of helicopter flights.