Olivia Newton-John fans voice their concerns after John Travolta was missing from her State Memorial

On Sunday, some of the biggest names in showbiz came together in memory of Dame Olivia Newton-John ... however, one notable person was missing.

As many A-list stars shared their memories of the beloved icon - who lost her decades-long battle with cancer in August - at her state memorial at Hamer Hall in Melbourne, there was no sign of John Travolta.

While the Hollywood superstars were an unforgettable pair on-screen and lifelong friends off, the actor didn't feature in person or via a pre-recorded message.

As the ceremony progressed, fans took to social media to voice their concerns, with one questioning: "Did I miss something from John Travolta ... I thought he was supposed to say something?"

"I need some explanation as to why John Travolta wasn't involved, yet he was mentioned to be doing something. I knew Delta was the last of the memorial but nothing from John Travolta, not even a video message. I hope he is okay," someone else wrote.

A third said: "Any thoughts why John Travolta didn't get a mention at all bar in the career highlights montage? No message, no mention?"

The beloved Grease star is yet to respond.

Newton-John is survived by her husband John Easterling and only daughter Chloe Lattanzi.