Like the movie Fallen in 1998 a movie was made in the 70's that was about the devil who took over people bodies and killed others. The ending was a helicopter crash at sea but the devil entered the body of a person who fell out just before it crashed.

Sounds like Satan's Triangle (http://www.imdb.com/title/tt0073662/reference)
YouTube (http://www.youtube.com/watch?v=Vn1sXOPmkQc)