Recent case of a QATAR Airways pilot who announced time to break the fast based on time in Doha, the destination. Muslim cleric on board took exception to this as according to him it's based on time of sunset at your present position.
He issued a religious order regarding this and told some passengers who had started eating that they would have to fast an extra day to make up for it.
BTW Have noticed some of our muslim cabin crew looking "distressed" by mid afternoon.