A man accompanying his sister-in-law while traveling

Q: Could you kindly explain to me the ruling on my wife traveling by plane from Al-Zhahran to Al-Ta'if in the company of her sister who is married to my brother, my brother and our little children. It is important to mention that I cannot travel to accompany her and get back because I do not have enough money to do so. Their parents will receive them in Al-Ta'if. It should also be mentioned that traveling only takes two hours.

A: It is not permissible for a woman to travel by plane or by any other means without a Mahram (spouse or permanently unmarriageable relative) because the Prophet (peace be upon him) said: A woman should not travel except with a Mahram. (Agreed upon by Al-Bukhari and Muslim) Her sister and sister's husband are not Mahrams to her. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.