It is permissible to fast or not to fast during Ramadan for one who is travelling for no sinful purpose, if his journey is two stages or further. But it is better for the one who is able to fast without suffering any harm to do so, and the one for whom it is difficult may break the fast Sahih Muslim 1113 d
Translation
A hadlth like this has been transmitted on the authority of Ibn Shibab who said that they (the Compnions of the Holy Prophet) followed the latest of his commands and looked upon it as one abrogating (the previous ones) and the most firm.