If you are travveling from Athens to Santorini there are 2 greek companies with flights for Thira (Santorini):

Olympic airlines

Aegean airlines

There are several greek ferry companies that can get you to Santorini, choose the one you prefer by visiting :

Blue star ferries

*Please note that there might be other greek ferry companies that can get you to Santorini depending on the year, because every once in a while there are different companies that handle the connection of Santorini island with Pireaus and Rafina port.

For international flights please check your air line company if they have a direct flight to Santorini.