There is no airport in Rethymno. Alternatively, you can travel to Rethymno by ferry. The closest airports to Rethymno are Chania and Heraklion. These two airports operate flights from/to Athens and Thessaloniki. Also in summer, they operate charter and low-cost flights from many European airports.
There is a frequent bus connection from Chania and Heraklion to Rethymno. Outside these airports, there are also many car rental companies.
Domestic Flights from/to Chania
Athens and Thessaloniki