Praise be to Allah the Lord of the Worlds.
The Muslim Ummah is unanimously agreed that a traveler is allowed not to fast in Ramadan, as indicated by the verse in which Allah Says (What means): "but if any of you is ill, or on a journey, the prescribed number (Should be made up) from days later." {Al-Baqarah, 184}. Another evidence is the Hadith in which the Prophet (PBUH) said: "Indeed, Allah Most High lifted (the fast) from the traveler" {Tirmithi}.
The majority of the Shafie, Hanafi and Maliki scholars stipulated, for allowing the person who is travelling for a long distance-more than 81 kms-not to fast, that the day of fast has already begun while on travel. In other words, that he leaves before dawn. Therefore, if he travelled during the day, then he isn`t allowed not to fast.
However, according to the reliable opinion of the Hanbali scholars, the traveler who is allowed not to fast is one who is travelling the distance at which it becomes permissible to shorten the prayers. Therefore, he is allowed to break his fast after he leaves the houses of the city. If he started travelling during the day (in Ramadan) and left the houses of the city, then he is allowed to break his fast, as indicated by the apparent meaning of the above verse and the narrations which explicitly addressed this matter.
For example, Ja'far ibn Jubayr said: I accompanied Abu Busrah al-Ghifari, a Companion of the Messenger of Allah (PBUH), in a boat proceeding from al-Fustat (Cairo) during Ramadan. He was lifted (to the boat), then his meal was brought to him. The narrator Ja'far said in his version: He did not go beyond the houses (of the city) but he called for the dining sheet. He said (to me): Come near. I said: Do you not see the houses? Abu Busrah said: Do you detest the sunnah (practice) of the Messenger of Allah (PBUH)? The narrator Ja'far said in his version: He then ate (it)." (Abu Dawoud). In addition, as it is allowed for the person who gets sick during the day in Ramadan to break his fast, it is permissible for the person who embarks on travel/journey during the day in Ramadan to break his fast.
Nevertheless, he isn`t allowed to break his fast before he embarks on travel as he is a resident. However, it is better for the person who travels during the day in Ramadan, while having made the intention to fast that day, not to break his fast. This is in order to get out of the controversy, and this is the view of the majority of the scholars since the outweighing view is that the person who is travelling during the day in Ramadan takes the ruling of the person who isn`t travelling/resident." {Kash-Shaaf Al-Khina`, vol.2/pp.312}.
If it was difficult for the person, who is travelling after dawn, to fast, and needed to do his job as perfect as possible, such as the pilot who is liable for the safety of the crewmembers as well as the passengers, then he is allowed not to fast in accordance with the permission granted by the Hanbali scholars. However, he must make up for each missed day after the month of Ramadan ends. And Allah the Almighty Knows Best.