How should a cabin crew member fast?
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.