DEHRADUN, India -- Ever since flash floods struck a mountainous area of northern India last week, 60 Indian military and civilian helicopters have been navigating fog, rain and treacherous Himalayan valleys looking for survivors and recovering bodies as part of the biggest airborne rescue and recovery operation in the history of the Indian military.
As of Tuesday, the operation had rescued more than 12,000 people, many of them Hindu pilgrims visiting holy shrines in the state of Uttarakhand, one of the worst-hit areas. The flooding, which began June 16, triggered by monsoons, has killed at least 1,000 and possibly many hundreds more.
But the rescue operation is not without hazards of its own. On Tuesday afternoon, a Russian-made Mi-17 air force helicopter crashed into a mountain, killing 19 aboard -- 5 airmen and 14 paramilitary members -- while returning from a mission in the Kedarnath Valley, a major pilgrimage center more than 11,000 feet above sea level, a spokesman for one of India's paramilitary groups said. Last week, another helicopter crashed in the same area, although no one died.
Pilots say the difficult terrain, adverse winds and absence of landing pads are testing their will and courage. "It is a warlike situation for us," said one pilot, Capt. Sandeep Soti. "We have been pushing our men and our machines beyond our capacities."
The paramilitary men on the Mi-17 had been building helipads, helping stranded people and digging bodies from the debris in the submerged town of Kedarnath for the past week. "These boys were among the first to land at Kedarnath to help pilgrims," said Deepak Pandey, a spokesman for one of the groups, the Indo-Tibetan Border Police. "They were coming home now."
Indian Air Force pilots have flown 1,400 times and evacuated more than 12,000 people since the flooding began, an air force spokeswoman, Squadron Leader Priya Joshi, said.
Many of the rescued are brought to Jolly Grant Airport in Dehradun, where the thumping of helicopter rotors has become the sound of hope for hundreds of relatives of the missing. On Monday afternoon, several men and women rushed toward the passengers alighting from a rescue helicopter. A few minutes later, they walked back, their faces a mix of resignation and disappointment, to wait for the next arrival.
Outside the airport, several relatives of the missing have been camping in tents. Vinayak Sonkar, a government employee from the western Indian state of Maharashtra, said he had been camping there for two days, hoping for news of his brother-in-law and his wife, who were stranded near the Kedarnath shrine after the flooding began.
"What can we do?" he said. "So many have died. They may be buried under the rubble. I am still hopeful, and that is why I am here."
Relatives have pasted the photos, names and addresses of the missing on the walls of the airport compound. They surround reporters and cameramen with photographs.
"The government should put up the photographs of the dead on its Web site," said Krishna Shah, a businessman from the western state of Gujarat who was looking for a cousin. "At least we would know who is dead and who might be alive."
The authorities prepared on Tuesday to cremate the bodies of hundreds of victims of the floods, The Associated Press reported. Wooden logs were loaded onto air force transport planes and flown to Kedarnath to be used in a mass funeral and cremation.
According to Indian officials, around 90,000 people have been rescued, but 5,000 are still waiting to get home. "We hope to rescue all stranded pilgrims by Friday," said V. K. Duggal, a member of the National Disaster Management Authority who is coordinating the rescue operation.
In an interview, Lt. Gen. N. S. Baba, who has been supervising 8,500 Indian Army soldiers in the operation, described one of the more difficult rescues, carried out in a very narrow valley on the trekking route to the Kedarnath shrine.
A pilot noticed around 100 people on the steep, forested upper slope of a hill, he said. Below, a river was overflowing. "There was no landing place," General Baba said. "The pilot negotiated the narrow valley and dropped four soldiers of Special Forces on the upper slope."
The soldiers prepared a landing space for a small chopper. As the stranded people noticed a hovering chopper, around 1,000 gathered. "We got them out," General Baba said.
On Monday morning, after dense fog reduced visibility and heavy rains continued, Air Chief Marshal N. A. K. Browne, the head of the Indian Air Force, addressed the stranded through reporters in the area: "Our helicopter rotors will not stop churning till such time we get each one of you out. Do not lose hope, and hang in there."
An investigation into the crash has been announced. "The pilots have been pushing themselves hourly beyond the normal flying limits," said Josy Joseph, a defense analyst and an editor with The Times of India. "If that turns out to be the reason for the crash today, it is a question that would hang for a long time on future operations."
Correction: June 26, 2013, Wednesday
This article has been revised to reflect the following correction: Because of an editing error, an earlier version of a picture caption with this article misidentified the location of Srinagar, where flood damage occurred. It is in the northern Indian state of Uttarakhand, not in Kashmir. (There is a Srinagar in Kashmir.)
This article originally appeared in The New York Times.