Releasing today, ALARACT 040/2021 includes revisions to published Grooming Policies authorizing women to wear ponytails in all uniforms on duty. https://www.army.mil/article/246037 

We made initial changes in Feb after a DOD-mandated review of our policies. Through feedback from the Force resulting in a clear, consolidated policy recommendation from a group of Soldiers, the Army has reconsidered the wear of ponytails.

Details are in the ALARACT, but in general - hair will be neatly and inconspicuously secured in a singular ponytail, two braids, or a singular braid and will not extend past the bottom of the shoulder blades when standing at the position of attention.

Additionally, ponytails are not required to be tucked into the Soldier’s uniform at any time, but should not hinder their physical performance or increase their risk to safety.