All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is religiously established that a woman is not permitted to travel without a husband or a Mahram (i.e. a person whom one is permanently prohibited from marrying due to suckling, marital, or blood relations). Many clear and authentic narrations were reported in this regard from the Prophet and this proves the importance of the matter. For more benefit, please refer to Fatwa 83795.
Therefore, none of you is permitted to travel without a Mahram.
If you refer to a safe company by mentioning the existence of a group of women during this travel, then this is irrelevant. Although the scholars differed in opinion about the permissibility of a woman travelling with a safe company in order to perform her obligatory Hajj, yet the opinion that prohibits it is a strong opinion. Therefore, it is more appropriate to rule this type travel as forbidden, as it is for entertainment. In addition to this, it is possible for a woman to entertain herself in her own town and there is no necessity or need for travelling abroad for entertainment.
If by travelling with Euro Star or by plane you refer to a safe method of travelling, then the reality proves otherwise. Indeed, such travel in this time and age is full of disadvantages, like a woman sitting beside a marriageable man, the plane being forced to land in another country, the delay of the time of departure, and the like or mockery that you could experience due to practising Islam and adhering to Hijab.
To conclude, the prohibition of a woman travelling without a husband or a Mahram includes any type of travel, whether it is a short or long trip, and whatever the means of transport is.