In the first place, we would like to stress that breaking the fast of Ramadan while traveling is a legal concession that portrays Islam’s tolerance and simplicity in matters of worship. The Prophet (peace and blessings be upon him) said: “Allah likes His servants to undertake the legal concessions given to them in the same way as He likes them to observe their obligations.” Although it is agreed that a traveler can break the fast of Ramadan, scholars differ concerning which is better for him; to break fast or to fast.
In this regard, we would like to cite for you the following fatwa issued by the eminent Muslim scholar Sheikh Yusuf Al-Qaradawi, in which he states the following:
“Jurists hold different opinions concerning which is better for a traveler; to keep his fast in Ramadan or break it. Abu Hanifah, Malik and Ash-Shafi`i maintain that it’s better for a traveler to fast in Ramadan, as long as he is able to fast and it doesn’t endanger him. They base their view on the fact that the Prophet (peace and blessings be upon him) used to fast in Ramadan while he was traveling, and the Prophet for sure chose for himself the highest degree of worship. Also, a person may disregard making up for the fast days of Ramadan that he breaks during his travel, then die without clearing himself of that obligation. However, it is a mistake to base this view on the Qur’anic verse that reads: “And that ye fast is better for you”, because this text is irrelevant to this situation.
Al-Awza`i, Ahmad and Ishaq, on the other hand, state that it is better for a traveler to break the fast of Ramadan, making use of the legal concession given to him. The Prophet (peace and blessings be upon him said: “Allah likes His servants to undertake the legal concessions given to them in the same way as He likes them to observe their obligations.” In some other narration he said: “Take Allah’s concessions which He has allowed for you.” Moreover, in the story of Hamzah Al-Aslami, the Prophet (peace and blessings be upon him) said: “It is good (for a man who is traveling) to break fast, and there is nothing wrong for one who likes to fast.”
`Umar ibn `Abdul-`Aziz, Mujahid and Qatadah said that the easier for the traveler the better. This is really a good view selected by Ibn Al-Munzir. Some scholars maintain that a traveler is free to choose between the two options, either to fast or break fast, and both cases have the same status. This maybe is supported by what Abu Dawud and Al-Hakim reported that Hamzah Al-Aslami said: “O Allah’s Messenger! I have an animal which I care for, use for traveling, and hire it. Sometimes Ramadan occurs (while I’m traveling) and I have the capacity to fast, and it’s easier for me to fast it at once than to postpone it, that it would be a debt on me.” The Prophet (peace and blessings be upon him) said: “Then do whatever you like.”
I myself prefer the opinion of the righteous Caliph `Umar ibn `Abdul-`Aziz (may Allah be pleased with him), because whenever the Prophet (peace and blessings be upon him) was given two options, he used to choose the easier. So, for a man who finds it easier to fast when people are fasting and difficult to make up when people are not fasting, it is preferable to fast. Conversely, if a traveler finds it difficult for him to fast while traveling, such as a person traveling on land, and it is easier for him to make up for the broken fast on other days, then he’d rather break fast. There are, by and large, certain considerations that make fasting the better choice and others which makes it better to break fast.”
Based on the above fatwa, we can conclude that you are best advised to follow the opinion which is easy for you keeping in mind that Islam is the religion of easiness. Allah Almighty says, “Allah tasketh not a soul beyond its scope.“ (Al-Baqarah 2: 286)
As for the time of imsak or iftar in case of fasting while traveling by plane for the whole daytime, the travelling one is to break his fast according the time of fast-breaking in the country from which he traveled. Once, he stays in another country, he has to follow the time of that country.