James Horner, a trained pilot, was reportedly alone aboard a small private plane, which crashed north of California’s Santa Barbara on Monday morning.
The plane crash left an impact crater and sparked a brush fire that had to be put out by firefighters, local fire authorities said.
His death was confirmed by Sylvia Patrycja, who is identified on Horner's film music page as his assistant.
She emotionally wrote on Facebook: “A great tragedy has struck my family today, and I will not be around for a while.
“I would like some privacy and time to heal.”
“We have lost an amazing person with a huge heart and unbelievable talent.
"He died doing what he loved. Thank you for all your support and love and see you down the road."
Celine Dion released a statement about his death, which read: “Rene and I are deeply saddened by the tragic death of James Horner.
"He will always remain a great composer in our hearts. James played an important part in my career. We will miss him.
"We offer his family and friends our deepest sympathy.”