A British climber whose mother was the first woman to reach the peak of Mount Everest in a solo climb has disappeared with his Italian counterpart while climbing Nanga Parbat in Pakistan, the ninth-highest mountain in the world.

The last time the Briton, Tom Ballard, and the Italian, Daniele Nardi, were heard from was on Sunday morning, when they had reached about 6,300 meters, or more than 20,600 feet, Mr. Nardi’s team wrote in a Facebook post on Wednesday.

“Every hypothesis and possibility is not overlooked,” the post said.

An aerial search-and-rescue operation for the two men was delayed after tensions between Pakistan and India flared into a military confrontation and Pakistani airspace was closed. But the Pakistani Army eventually sent a helicopter to the men’s last-known location on a reconnaissance flight on Thursday. Rescuers found no trace of either climber, Mr. Nardi’s team said.

A helicopter was expected to undertake a second reconnaissance flight later on Thursday.

Mr. Ballard and Mr. Nardi are both experienced mountaineers. Mr. Ballard was dubbed “King of the Alps” by the British news media after he became the first person to climb the notoriously perilous six great north faces of Europe’s highest mountain range solo in a single season.