Travel by train instead of flying
Depending on the starting point, different destinations can be reached within a certain time across Europe. The interactive map Chronotrains shows how far you can travel from any station in Europe in less than 5 hours.
To book a specific train trip, various booking portals can be used, such as:
The FAQs contain a lot more information on the topic of flight reduction and on the FlyingLess project itself.