In the still, quiet hours of a Florida morning, John Travolta casts a lonely shadow. Another sleepless night has brought him to his private tarmac, where he loses himself in his dark heartbroken thoughts.

Here, away from the glare of Hollywood stardom, John is a shattered, sad-faced father — a hurting man hopelessly lost since the sudden death of his only son, Jett. He spends hours deep in thought, sometimes aimlessly driving a golf cart back and forth.

Friends say his grief is driving him deeper into a lonely shell, and seemingly distancing him further from his wife Kelly Preston.

It's an eerie scene, and one his concerned neighbours at the exclusive estate built around a private airport say is becoming all too frequent.

All the trappings of fame — his immense wealth and vast collection of aeroplanes — can't soften his raw-edged misery.

At 55 years of age, John Travolta appears a broken man, crumbling beneath unspeakable grief.

While he spends much of his time in solitude with the curtains drawn, or on lonely golf cart rides in the darkness of early mornings, Kelly is also dealing with Jett's death by throwing herself into her work.

"After Jett died, John and Kelly were totally bonded by their shared grief," an insider close to the star couple says. But now they are coping very differently, which is creating "a gap between them that seems to be growing".

"John wants to be alone. He has secluded himself in his Florida home, where he spends his time watching old movies and eating comfort foods like ice-cream. He stays in bed a lot and cries by himself. He cries every day and he's not doing well," says the source.