Praise be to Allah.
The scholars are of the view that the fast lasts from dawn until sunset, because Allaah says (interpretation of the meaning):
“and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night), then complete your Sawm (fast) till the nightfall”
And it is proven that the Prophet (peace and blessings of Allaah be upon him) said: “When night comes from here and departs from here, and the sun sets, then the fasting person breaks his fast.”
Every fasting person is subject to the ruling of the place where he is, whether he is on the ground or in a plane in the air.
Based on that, if a person breaks his fast whilst on board a plane according to the timetable of some city although he knows that the sun has not set, then his fast is invalid, because he has broken his fast before the sun has set for him, and he has to make up that day.