the messenger of allah pbuh traveled in ramadhan and sometimes observed fasting and sometimes broke his fast. he pbuh gave his companions the option to do either, but he would order them to break their fast when they approached an enemy in order to be strong for battle. when the journey did not involve jihad, allah's messenger told them it was facilitation, so whoever took advantage of it – it was good, and whoever preferred to fast was not to be blamed. he traveled in ramadhan for two of the greatest campaigns: that of badr and the conquest of makkah.
it was not of his guidance to designate a specific distance beyond which a traveler could break his fast, and nothing authentic was related in this regard. when setting out on a journey his companions did not stipulate passing beyond the town's residential area as this was not from the sunnah.
ubayd ibn jabr reported: "i boarded a ship from fustat with abu basrah al-ghifari, a companion of allah's messenger pbuh, during ramadhan. we had not yet left the settlement behind when he called for a meal, saying, 'come.' i said, 'don't you see the houses?' abu basrah said, 'are you disinclined to the sunnah of allah's messenger?'" (ahmad and abu dawud)
muhammad ibn ka`b said, "i went to anas ibn malik –may allah be pleased with him- in ramadhan. he intended to travel so his camel had been prepared and he had worn his traveling clothes. he ordered some food and ate, so i said to him, 'is it a sunnah?' he said, 'it is a sunnah,' and mounted." (at-tirmithi)
these narrations clearly show that whoever begins a journey during a day of ramadhan may break the fast.