Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
It is permissible for a person traveling by plane to break his fast when the sun sets at his location. He is not to break his fast according to the [local] time of the country of his departure or that which he is flying over but when he sees that the whole disk of the sun has set.
Answering your question, Dar Al-Ifta Al-Missriyyah, states:
It is permissible for a person traveling by plane to break his fast when the sun sets at his location. He is not to break his fast according to the [local] time of the country of his departure or that which he is flying over but when he sees that the whole disk of the sun has set.
If it becomes difficult for the traveler to continue his fast, he is to break it due to the excessive hardship posed by travel and not because the fasting hours have ended; and he must make up the day on which he broke his fast.
The in-flight announcements made by some pilots concerning breaking the fast according to the local time of the country of departure or the plane’s current location without giving heed to seeing the sun set is legally invalid. A fasting person is to break his fast when the sun first sets and is to ignore its subsequent appearances and disappearances which occur due to the plane’s speed.
Almighty Allah knows best.
Source: http://www.dar-alifta.org/Foreign/ViewFatwa.aspx?ID=535