If a traveller knows such a situation already he should not keep fast, it is lawful to skip fast during journey. However, if one kept fast and the day lengthened beyond normal day that he felt unbearable hunger or thirst then such a person may break the fast during flight. Such a person will only make qadha of the missed fast, not kaffarah. He will also make qadha of the 4 or 5 salah which he missed during journey.
Allah knows Best!
Darul Uloom Deoband