The ex-couple were spotted walking a talking together as they left Burbank Airport after attending a tech conference in San Jose.
According to a US showbiz website, the A-listers even flew back from the conference together, on the same plane.
The site reported that Demi, 50, and Ashton, 35 seemed ‘cordial, if not friendly’ but saw the rare public sighting as a sign that they will soon reach a divorce settlement.
As a woman, a mother and a wife, there are certain values and vows that I hold sacred
The couple split in late 2011 after claims the Ashton - who is now dating 30 year-old actress Mila Kunis - cheated on Moore with Sara Leal during a trip to San Diego on his wedding anniversary.
He filed for divorce in December 2012 but proceedings have been stalled since Demi allegedly demanded an £18million settlement ‘to compensate’ her for ‘emotional turmoil.’
First announcing her split from Ashton in 2011, Demi said the decision came with a ‘great sadness and a heavy heart.’
‘As a woman, a mother and a wife, there are certain values and vows that I hold sacred, and it is in this spirit that I have chosen to move forward with my life,' she added.
Their divorce is one of the most expensive in Hollywood – with Ashton being TV’s highest-paid actor and worth a reported $140 million, while Demi is worth a reported $150 million.
Demi originally received a reported $90 million when she divorced Bruce Willis.