Praise be to Allaah.
So long as you are working as a member of the cabin crew in an airplane, you are
travelling, and the scholars are agreed that it is permissible for the traveller to break his fast during Ramadaan, whether it is difficult for
him to fast or not.
It is preferable for the traveller to fast, so long as fasting does not cause him
hardship, in which case it is better for him to break his fast and make up the days that he did not fast later on. See Question no.
20165.
If you want to fast then you have to refrain from eating and drinking etc from
dawn in the place where you are at the time of dawn, whether you are on the ground or in the air.
Similarly the ruling concerning iftaar is that you should not break your fast
until the sun sets in the place where you are. If you are on board the plane and you can see the sun, it is not permissible for you to break your
fast until the sun sets, even if the sun has already set for the people of the land which you are flying over in the plane.
The fact that the day may be made longer or shorter because of travelling does not
have any effect on the fast.
It is well known that if you are travelling eastwards, the day will become shorter
for you, and if you are travelling westwards the day will become longer.
What matters is the place where you are at the time of dawn and the time of
sunset.
See also question no. 38007.