"About 11.30am today, two bushwalkers alerted emergency services to advise they had come across a man who identified himself as Jamie Neale near the Narrow Neck fire trail, near Katoomba," NSW Police said in a statement.

"Police Rescue officers, using a Rural Fire Service vehicle, made their way to the location and confirmed the identity of the man.

"He's been taken to Katoomba Hospital for treatment of dehydration and exposure."

One of the bushwalkers had some medical experience and treated Mr Neale before he was taken to hospital, 2GB Radio reported.

Mr Neale told a police officer at the hospital that he had been worried the searchers had given up looking for him, 2GB said.

A 2GB reporter said that, at the hospital, Mr Neale looked very haggard and had answered questions "mumbling". "[He's] walking, talking and now in hospital care," he said.

"He was a bit shocked that there were TV cameras there. [But] he ... didn't look like he was about to fall over."

Mr Neale's father, Richard Cass, was at Sydney Airport and about to fly home to Britain this afternoon, a police spokesman said.

"My understanding is he's now being flown [by helicopter] from the airport to the Blue Mountains ... he was at the airport to fly out of the country," he said.

Mr Neale, 19, from North London, had been missing since July 3, and was last seen above Ruined Castle, a rock formation in the Jamison Valley, about midday, police said.

A massive search had been mounted for Mr Neale, who had left many of his possessions, including a mobile phone, at the youth hostel in Katoomba where he had been staying.

He was seen leaving the hostel, intending to walk the popular track to the Ruined Castle rock formation and was last sighted hours later on top of it.

He told a married couple he met there that he intended to keep walking to Mount Solitary, a return trip of about 10 hours.

Police had expressed frustration Mr Neale did not register his plans with police or the National Parks and Wildlife Service before setting out on July 3.

Police also urged bushwalkers to use personal locator beacons that are available free of charge from Springwood and Katoomba police stations and the National Parks and Wildlife Service.

Police had said finding Mr Neale was "like searching for a needle in a haystack".

On Monday, they said the chances of finding him alive were slim.