Bus, S-Bahn or long-distance train: Missed flight due to public transport delays. As a passenger you are usually stuck with the costs.
Stuttgart Airport recommends that travelers should arrive at the airport properly two hours before departure, but in no case more than three hours beforehand. The ADAC advises passengers to plan a time buffer, especially when traveling by long- distance train. Local trains would be a lot more punctual. Here, too, you shouldn't leave at the last minute, but you usually don't run the risk of arriving several hours late.