This was pointed out a couple of weeks ago - not so much for the fact that Denver died in an air crash but for the fact that the song "Leaving on a Jet Plane", as any fule no, is about someone who DOESN'T want to fly ANYWHERE, (hence the lyric 'Oh babe, I'd hate to go'...conveniently muffled during the ad).
All told it seems a peculiar choice of music for an airline. You wouldn't use Elvis' "Heartbreak Hotel" to promote the Hilton, would you?