There are a number of buses per day between the four main cities. The buses between Heraklion, Rethymnon and Chania run hourly from 5.30 am (first departure from Chania and Heraklion) to 8.30 pm (last departure from Chania and Heraklion). This can pose a problem for night arrivals at the airports. The travel between Chania and Heraklion takes about two and a half hours.
Most of the buses have air-conditioning and are recent brand models. Travelling by bus is the most safe way in crete as the accidents are very rare.
For buses timetables please refer to this link: