'Titanic' Composer James Horner Dead in Plane Crash

Horner's assistant Sylvia Wells confirmed his death on Facebook, writing, "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."

Celine Dion tweeted about his death, writing, "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."

A plane owned by James Horner -- the Academy Award-winning composer of "My Heart Will Go On" -- crashed Monday morning, killing the pilot.

Law enforcement sources tell TMZ ... the 2-seater S312 Tucano MK1 -- a single-engine turboprop -- went down at 9:30 AM west of Santa Barbara. We're told the pilot was alone in the aircraft when it crashed, but authorities have not identified the body.

The crash sparked a brush fire, and there was almost nothing left of the plane.

Horner composed soundtracks for Hollywood's top directors – Stephen Spielberg, George Lucas, Ron Howard, Mel Gibson -- and won an Oscar and a Golden Globe for "Titanic" ... which included Celine Dion's massive hit.

61-year-old Horner is a known recreational pilot ... much like Harrison Ford.