Is it permissible for a girl to travel with her mother and siblings for Hajj and Umrah without a mahram (unmarriageable kin) for the purpose of work, relying on the principle of "safe companionship," and is it permissible to travel by plane for Umrah in Ramadan and then return?

The majority of scholars prohibit a woman's travel without a mahram (unmarriageable kin) except out of necessity. Some, however, permit it if she is safe or if the journey is for an act of obedience. Based on this, if your journey is safe, you may adopt the view of those who permit travel without a mahram for performing 'Umrah or visiting family, especially given the necessity and the difficulty of bringing a mahram along.