Merrell and Standefer vanished last weekend after losing their footing while crossing a creek near the North Rim. They were on a hike with Merrell's husband, Merrell Boot Co. co-founder Randy Merrell, and the boy's mother.



The park soon scaled back the operation and stopped using the drones but continued the search. In a statement, the hikers' families backed the decision and said they were "still praying for a miracle."



The drones have been used a few times already.



In November, after a visitor drove off a cliff and died, drones were sent in to examine the trees and brush and make sure it was safe for a helicopter to fly in and lift the car out.



The next month, rangers used a drone to locate a woman who had jumped to her death. Then they rappelled down to retrieve the body.



The dangers of flying choppers in the canyon were illustrated in 2003, when a Park Service helicopter experienced a mechanical failure and crash-landed on the North Rim. Those aboard suffered only minor injuries; the helicopter was totaled.



Other national parks use drones, but for wildlife research. The use of private drones is prohibited in national parks.



James Doyle, a spokesman for the park service's Intermountain region, said other national parks will probably seek their own drone fleets, too. He said the Grand Canyon's extreme topography — it is a mile deep — makes it a perfect candidate.



"It's a wonderful tool for the unfortunate situation we just found ourselves in at Grand Canyon," Doyle said.