I was wondering if I was allowed to fly on Tisha B’av after Chatzos? And what are the Halachos about breaking the fast?

Allowed, but not recommended, since:

a) Lechatchila, one should avoid traveling (especially flying) on a fast day, due to concerns such as the risk of dehydration, c”v;

b) One is to avoid traveling in the Nine Days, and especially on Tisha B’av (see also here);

c) A fast day is meant for introspection and Teshuvah, and one should avoid regular activities that distract from its purpose, particularly on Tisha B’Av, when we are also not to divert from the day’s mourning.

When flying on a fast day, one is to break the fast only once it becomes nightfall in one’s current location. (When flying westward and it’s a pressing situation, there is some room for leniency to break the fast at the time of nightfall in the place of departure – see here).

(This potential complication with the fast’s end time is another reason to avoid flying that day if possible).

ולהעיר מאג״ק מוהריי״צ טו ע׳ לז.

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