Five international Airports located in a range of 100 Km:

• Frankfurt am Main is the major international airport in Germany and of largest in Europe, with internal train station served with direct train to Heidelberg.
• Karlsruhe and Stuttgart are also international airport advised for continental flights. 
• Saarbrucken and Frankfurt-Hahn are served by low cost companies over Europe.

Train connections are provided by most of the airports to reach Heidelberg main station ( 20-30 Euro). They can be booked here: https://www.bahn.com/en .