Shafaqna English- Islamic laws on fasting according to the Fatwas of the Grand Ayatollah Sistani.
Laws of fasting for travelling before or after Zuhr/Dhuhr
Ruling 1690: If a fasting person travels after Zuhr, he must, based on obligatory precaution, complete his fast; and in such a case, it is not necessary for him to make up that fast. If he travels before Zuhr, then based on obligatory precaution he cannot fast on that day, particularly if he had made the intention to travel the night before. In any case, he must not do anything that invalidates a fast before reaching the permitted limit (Hadd Al-Tarakhkhus), otherwise Kaffarah becomes obligatory on him.
The full text of the Islamic Laws according to the Fatwas of the Grand Ayatollah Sistani is available in English here:
https://www.sistani.org/english/book/48/
In French:
https://www.sistani.org/french/book/55/
In Spanish: