Originally Posted by
Flying Lawyer
long distance buses do with some exceptions not exist in Germany).
Direct services to and from airports tend to be among these exceptions (HAM - an airport I use quite regularly - has direct bus links to both Lübeck and Kiel, and I note that STR has a direct bus to Tübingen).
However, as you said, there appears to be no direct bus from STR to Heilbronn at the moment.