Ruling on a woman revealing her face when traveling abroad

 If a woman travels abroad, what is the ruling on hijab with her face uncovered?

A woman outside, like inside, does not have the right to uncover her face. Rather, she must cover herself inside and outside; Because God Almighty said: And when you ask them for anything, ask of them from behind a veil. That is purer for your hearts and for their hearts. [Al-Ahzab: 53] 
And God Almighty said:And they should not display their adornment except to their husbands or fathers. [An-Nur: 31] They must cover and veil themselves at all inside and outside; Because men on the outside, like those on the inside, fear temptation for them, and women also fear temptation for them. The bottom line is that the inside and outside are equal in the obligation of hijab.