Climbers Tom Ballard and Daniele Nardi were last heard from on February 24 as they climbed the “Killer Mountain”, which at 8,125 metres (26,660 feet) is the world's ninth-highest peak.
They were attempting a route that has never before been successfully completed.
Two helicopters flew a Spanish climbing team from the base of K2 -- the world's second highest mountain -- to Nanga Parbat Monday afternoon to look for the missing climbers, according to a top army aviation official.
He said the helicopters carried out an aerial search with the help of mountaineer Rehmatullah Baig -- who was climbing with the missing men before turning back -- but could not find anything.
"The helicopters flew for more than 30 minutes in the targeted area but there was no sign of life," the official said, requesting anonymity.
Baig said the Spanish team would begin a search with drones on Tuesday.
Ballard is the son of British mountaineer Alison Hargreaves, the first woman to conquer Mount Everest solo and without bottled oxygen.
She died descending K2 in 1995.
The search was delayed because rescue teams were forced to wait for permission to send up a helicopter after Pakistan closed its airspace on Wednesday in response to escalating tensions with India.
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