Travolta shared a photo of a young Newton-John to his social media pages, along with a heartfelt message.
"My dearest Olivia, you made all of our lives so much better," he wrote. "Your impact was incredible. I love you so much. We will see you down the road and we will all be together again. Yours from the first moment I saw you and forever! Your Danny, your John!"
Newton-John's husband, John Easterling, broke the news of her passing Monday, sharing to her social media pages, "Dame Olivia Newton-John (73) passed away peacefully at her Ranch in Southern California this morning, surrounded by family and friends. We ask that everyone please respect the family’s privacy during this very difficult time."
"Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer. Her healing inspiration and pioneering experience with plant medicine continues with the Olivia Newton-John Foundation Fund, dedicated to researching plant medicine and cancer," the message continued, also paying tribute to the family and friends the actress left behind. "In lieu of flowers, the family asks that any donations be made in her memory to the @onjfoundation."
Newton-John paid tribute to Preston at the time, writing, "@therealkellypreston was a radiant, warm and gentle spirit - a loving, devoted wife, mother and sweet friend. My heart breaks for John, Ella and Ben. No words can express my sorrow for her family. Kelly’s light shines on in her beautiful children. Xox."