This guy wanted an enduring mystery. Hence he did not want the plane to randomly crash after fuel exhaustion. There was always the small chance this would be seen by a stray fishing trawler or yacht or other vessel.
Hence you can make 2 probable assumptions
1. Conscious and in control until the end
2. The water would have been sufficiently dark that ships running lights would have been visible.
Did he ditch, or a high speed dive? If a controlled ditching to reduce fragmentation and debris, then he would have needed some early daylight.
So pretty close to the solar terminator - perhaps a bit west of it so he had some twilight but not yet sunrise.