Pilot reveals Cleo search 'wasn't looking good' from day one

As the desperate search for missing WA girl Cleo Smith enters its 10th day, a chopper pilot who led the search from the air has admitted things did not look good just hours into day one.

Justin Borg put his chopper into the air mere hours after Cleo was first reported gone from her family's tent at a campground in the tiny town of Carnarvon.

Speaking on Today, Mr Borg said he expected to spot the four-year-old from his helicopter that morning, given the stark, open terrain.

Helicopter pilot Justin Borg said he expected to find young Cleo in just hours on day one.

"First of all … we thought it was just going to be a matter of her wandering off, that we would have found her very quickly," he said.

"Once we hadn't located her after an hour it wasn't looking good."

Mr Borg said a team of experienced stock musterers had been working the ground, while his chopper flew sorties up and down the coastline, looking for Cleo, clues or the young girl's sleeping bag.

"We look under every stone and do not leave a stone unturned," Mr Borg said.

"We know the area well."

His chopper at times hovered just metres above the ground to double-check partially concealed spots or rule out potential clues of significance.

Mr Borg said he hopes for the best but it now seems unlikely Cleo just wandered off from the tent.

Mr Borg responded to calls to help on the first day.

His chopper and a light plane remain on stand-by if needed to fly more missions by police.

"We are still hoping for a positive outcome," he said.

Police have now shifted away from a possible theory that Cleo simply wandered off from her tent, in the early hours of October 16.

Cleo was staying inside the tent with her mum, Ellie, her mother's partner Jake Gliddon and baby sister Isla.

Mr Borg described the coastal terrain as 'fairly open' with low-lying shrub, which would be 'slow travelling' for a girl aged just four. The search for Cleo Smith has entered its fifth day. Pictured are the pyjamas cleo was wearing the night of her disappearance and a similar sleeping bag.

Mum's plea for help

Ms Smith today posted another heartbreaking message on Instagram, along with pictures of Cleo and Isla together, asking the question "where are you baby" with two broken heart emojis.

"We all need her home," Ms Smith wrote on another image, following a reminder that the Western Australia government has posted a $1 million reward for information about her missing daughter.

Alongside another photograph of Cleo and Isla, Ms Smith wrote: "Best big sister ever."

Police are now focusing on a crucial window between 1.30am and 6am.

Ms Smith said Cleo woke for a drink of water at 1.30am, but that she was gone when the family woke up in the morning.

There has been no sign of her since.

One zip to the tent was reported to be at least partly open, beyond the reach of Cleo, and her sleeping bag was also missing from inside the family tent.