It is not permissible for a woman to travel for Hajj except with a mahram
Question

Is it possible for a women to go to hajj or umrah in a group of people or in a group of women if there is no mahram willing to go with her?.
Praise be to Allah.The scholars, past and present, differed concerning this issue. Some of them said that it is permissible for a woman to travel for Hajj without a mahram if the road is safe and she is with a trustworthy group. 
Some of them said that it is not permissible for her to travel except with a mahram who can protect her, even if she is with a trustworthy group. This is the view of Abu Haneefah and Ahmad. They quoted the following as evidence: 
1 – It was narrated that Ibn 'Abbaas (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah be upon him) said: “No woman should travel except with a mahram, and no man should enter upon a woman unless there is a mahram with her.”  A man said: “O Messenger of Allah, I want to go out with such and such an army, and my wife wants to go for Hajj.” He said: “Go for Hajj with her.” Narrated by al-Bukhari (1763) and Muslim (1341). 
2 – It was narrated that Abu Hurayrah (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah be upon him) said: “It is not permissible for a woman who believes in Allah and the Last Day to travel for the distance of one day and one night except with her mahram.” Narrated by al-Bukhari (1038) and Muslim (133). According to al-Bukhari (1139) and Muslim (827), from the hadeeth of Abu Sa’eed: “The distance of two days.” 
Ibn Hajar said: 
In the hadeeth of Abu Sa’eed it is limited to “the distance of two days” and in the hadeeth of Abu Hurayrah it is limited to “the distance of one day and one night.” There are also other reports. In the hadeeth of Ibn ‘Umar it is limited to “three days” and there are other reports too. 
Al-Nawawi said: The apparent meaning of this definition is not what is meant, rather everything that is regarded as travel is forbidden to a woman unless she has a mahram with her. The definition of the limits was in reference to specific incidents. Ibn al-Muneer said: The differences in the definitions arose because there was different questioners in different situations. 
End quote. 
Fath al-Baari (4/75). 
Secondly: 
Those who say that a mahram is not required quoted the following as evidence: 
1 – It was narrated that ‘Adiyy ibn Haatim (may Allah be pleased with him) said: Whilst I was with the Prophet (peace and blessings of Allah be upon him), a man came to him and complained of poverty. Then another came and complained about banditry. He said: “O ‘Adiyy have you seen al-al-Heerah?” I said: “I have not seen it, but I have been told about it.” He said: “If you live a long life, you will see a woman travelling from al-Heerah until she circumambulates the Ka’bah, fearing no one but Allah.” … ‘Adiyy said: And I saw a woman travelling from al-Heerah until she circumambulated the Ka’bah, fearing no one but Allah. 
Narrated by al-Bukhari (3400). 
This argument may be countered by noting that this was simply the Prophet (peace and blessings of Allah be upon him) foretelling this incident. Speaking of an incident does not mean that it is permissible. Rather it may be permissible or not, depending on the shar’i evidence. The Prophet (peace and blessings of Allah be upon him) also foretold that drinking alcohol, zina and a great deal of killing would become widespread before the Hour begins, and these are things that are forbidden and are major sins.
What is meant by the hadeeth is that security would become widespread, so that women would feel emboldened and one of them would travel without a mahram. It does not mean that it is permissible for a woman to travel without a mahram. 
Al-Nawawi (may Allah have mercy on him) said: Not everything that the Prophet (peace and blessings of Allah be upon him) foretold as signs of the Hour is haram or forbidden. If the shepherds compete in erecting tall buildings, and wealth becomes widespread, and there is one man to look after fifty women, these things are undoubtedly not haram. Rather these are signs, and a sign has nothing to do with whether it is halaal or haram. Rather a sign may be good or bad, permissible or haram or obligatory or anything else. And Allah knows best. End quote. 
It should be noted that the difference of scholarly opinion regarding the necessity of having a mahram in order to perform Hajj applies to the obligatory Hajj only. As for naafil (supererogatory) Hajj, the scholars are all agreed that it is not permissible for a woman to travel except with a mahram or husband, as it says in al-Mawsoo’ah al-Fiqhiyyah (17/36). 
The scholars of the Standing Committee said: A woman who does not have a mahram is not obliged to perform Hajj, because having a mahram is part of being able for it, and being able for it is one of the conditions of Hajj being obligatory. Allah says (interpretation of the meaning): 
“And Hajj (pilgrimage to Makkah) to the House (Ka‘bah) is a duty that mankind owes to Allah, those who can afford the expenses (for one’s conveyance, provision and residence)”[Aal ‘Imraan 3:97]
It is not permissible for her to travel for Hajj or anything else unless she has her husband or mahram with her. This is the view of al-Hasan, al-Nakha’i, Ahmad, Ishaaq, Ibn al-Mundhir and Ashaab al-Ra’y, and this is the correct view, because of the verse quoted above as well as the general meaning of the ahaadeeth which forbid a woman to travel without her husband or mahram. Maalik, al-Shaafa’i and al-Awzaa’i disagreed with that and they stipulated conditions for which they do not have any proof. Ibn al-Mundhir said: They ignored the apparent meaning of the hadeeth, and each of them stipulated conditions for which they did not have any proof. End quote. 
Fatawa al-Lajnah al-Daa’imah (11/90, 91). 
They also said: 
The correct view is that it is not permissible for her to travel for Hajj except with her husband or her mahram. It is not permissible for her to travel with trustworthy women without a mahram, or with her paternal aunt, maternal aunt or mother. Rather it is essential that she be with her husband or a mahram. 
If she cannot find someone to accompany her, then she is not obliged to do Hajj so long as that is the case. 
End quote from Fatawa al-Lajnah al-Daa’imah (11/92). 
And Allah knows best.