Rav Aviner does not permit any kind of pants for women under any circumstances, not even pajamas!
However, many other dati poskim are more meikel. The Religious Zionist kibbutz movement specifically permits them.
It should be noted that modern trousers did not make it to the Ashkenazic Jewish world until about 200 years ago. They had been commonly worn in the Sefardic world by Muslim women long before. In America, women and men both started wearing trousers and overalls on a regular basis, except in cities, at about that time. I have seen century-old photographs of female railroad workers for the Southern Pacific railroad; every woman is in trousers or overalls (they looked like loose denim, but I could not be absolutely sure because they were black and white photos).