Inside Olivia Newton-John and John Travolta's 'Wonderful' Friendship After 'Grease': We 'Share a Bond'

John Travolta and Olivia Newton-John enjoyed an enduring friendship over the years since making Grease together.

The costars sang and danced opposite each other as Danny and Sandy in the classic 1978 movie musical. In the decades since they have supported each other through tragedy and major life milestones. They even reunited and dressed up as the iconic lovebirds during the Meet n' Grease sing-along event at the Coral Sky Amphitheater in West Palm Beach, Florida, back in December 2019.

"We did something life-changing, making that film," Newton-John told PEOPLE back in 2018 on the film's 40th anniversary. "[At the premiere] you got the feeling from the energy that something was happening. It was a huge response. I feel grateful to be a part of that and to have worked with him. We've stayed friends ever since."

"[In tough times] John always reaches out to me," she added, as Travolta said, "When you share that kind of meteoric success — and nothing has been able to exceed it — you share a bond. I've been through her having a child, getting divorced, losing her sister. She's been through my getting married, having children. It's wonderful and full of shared memories."

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Dennis Stone/Mirrorpix/Getty In 1978

Travolta, who also co-starred with Newton-John in the 1983 film Two of a Kind, also said, "Olivia's quite a ­spectacular human being. She's worthy of good friendship."

On Monday, Newton-John's husband John Easterling announced via her Instagram page that the singer/actress died peacefully at her Ranch in Southern California earlier in the morning. She was 73.

John Sciulli/Getty John Travolta and Olivia Newton-John at the 2018 G'Day USA Black Tie Gala on Jan. 27, 2018.

Travolta, 68, wrote on Instagram, "My dearest Olivia, you made all of our lives so much better. 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 moment I saw you and forever! Your Danny, your John!"

Alberto E. Rodriguez/Getty In 2018

Years after Newton-John announced in May 2017 that she was diagnosed with breast cancer that had metastasized to the sacrum, Travolta showed support when asked about her at a red carpet event in 2019. "She looks incredible," he told Entertainment Tonight at the time. "She doesn't look any different than [she did] years ago, and I'm very proud of her."

Earlier this year, when Travolta shared a photo with son Ben, 11, and daughter Ella, 22, on New Year's Eve, Newton-John complimented them in the comment section. "Ella you look stunning and classy! The dress is gorgeous. Wishing you and Ben and Dad a Healthy happy New Year ❤️."

Ron Galella Collection/Getty In 1992

Travolta shares his kids with his late wife, actress Kelly Preston, who died at age 57 in 2020 following a two-year battle with breast cancer. Later that year, Newton-John remembered Preston on PEOPLE (the TV Show!) as a "radiant, beautiful light in the world" and said Travolta was doing "as well as it can be expected when you just lost your love, your wife and the mother of your children."

Preston's death "really strengthened my resolve" to form the Olivia Newton-John Foundation, she added, "because I've lost way too many friends to cancer, family members and friends. Having lived with it, this is my dream. This is my passion to see a world beyond cancer."