These are the valid reasons for breaking the fast during Ramadan: 1- sickness, 2- traveling, 3 - pregnancy and breastfeeding, 4- senility and old age, 5- intense hunger and thirst, and 6- compulsion.

It is permissible for a fasting person to break his fast if he travels during the day. For more, please see the detailed answer.

It is haram for a traveller to break his fast when: 1- he is travelling but the distance does not reach the distance at which it becomes permissible to shorten the prayers, 2- his journey is not permissible, 3- he is travelling in order to break the fast, and 4- he is travelling and wants to break the fast before leaving the houses of his village or city.