Concession for a traveler to skip fasting during travel.
In the blessed month of Ramadan, missing a fast in the state of travel with the intention that the makeup (Qaza) fast will be kept after Ramadan is permissible, provided that the travel is at the distance of Shari travel (Safar-e-Shar'i); however, if there is no severe hardship, then keeping the fast itself is preferred. (Kitab-un-Nawazil/Vol:6/Page:337)