I agree, the circumstances are VERY strange, to say the least.
But remember that we dont have, and will never have, all the information. Did the poor guy just find out from his MD that he had inoperable cancer? Had he been started on a new med(s) that changed his outlook?
Did he know something that was not to come out?
That being said, the method of death was odd.......I am sure that it could be done alone, but why????
Exactly, why would the family be so willing to accept a suicide and not demand an investigation? We have only the family's word that he set out alone. Maybe he did. But did he pick up a passenger along the way (willingly or not)? I just find it highly unlikely that the family would just accept this suicide theory without an objection. There are just too many "why would he" to this story.