Claire Hockridge and Phu Tran have been missing in a remote area south of Alice Springs in the Northern Territory for the past 13 days.
Rescue efforts have been ramped up, with two helicopters deployed at first light today to cover an area 23km from the Stuart Highway where it is believed the pair may be.
One of the three missing people, Tamra McBeath-Riley, was found during an aerial search yesterday with the car the trio was travelling in, bogged in the Hugh River.
Ms McBeath-Riley was found in a stable condition, having kept hydrated by boiling and drinking groundwater found nearby.
She was taken to the Alice Springs Hospital for observation.
Police have found a set of footprints they hope will lead them to the missing pair.
Search crews are following those footprints, hopeful of finding Ms Hockridge and Mr Tran alive.
Alice Springs Superintendent Pauline Vicary said the friends initially waited with their stranded car, but two days later after no-one came looking for them, they abandoned the vehicle, leaving a note inside to indicate the direction they were heading.
The group walked about 1.5km west, where they found puddles of groundwater from unseasonal showers that have fallen over the dry river system in the past fortnight.
Supt Vicary said for one desperate week they stayed together, gathering the dirty water, boiling it when they could and using a shirt to strain out the sediment.
Again they waited for help but when none came, they decided to split up.
Ms Hockridge and Mr Tran, who had a TomTom device for navigation and a compass, headed north, towards the Stuart Highway, about 20km away.
“We do know that they have left together. We have located one set of footprints which we are now focusing our search area on. But we have not located the second one at this stage,” Supt Vicary said.
“It’s quite a diverse terrain. There’s sandy dunes, there’s hard clay, there’s areas of dense trees, but there are also rocks and rangers in the area.”
She said the group had little food with them – some biscuits and some beef noodles, which would not have lasted long.
Temperatures have nudged 40C in recent days.
– with AAP