Which country should be observed for the sighting of the new moon of Ramadan, bearing in mind that the questioner will be on an airplane between Munich and Muscat on the night of the 30th of Sha'ban?

If the sun sets upon you while you are in Germany, then ascertain the crescent moon there. If it is not confirmed, then the ruling is based on Sha'ban. If you arrive in Oman and the crescent moon has been confirmed there, then act according to what has been confirmed by them. The consideration is given to the country where the sighting of the Ramadan crescent moon has been confirmed and where you are present, due to Allah's saying: "So whoever sights [the new moon of] the month, let him fast it," and due to the Prophet's (peace be upon him) saying: "Fast when you see it (the new moon), and break your fast when you see it."

Sheikh Ibn Uthaymeen said: If you are in a country and you do not know whether they have seen the crescent moon or not, then base your action on the original principle. If you are in Sha'ban, fasting is not obligatory for you. If you are in Ramadan, do not break your fast. The consideration is given to the place where you are.