Generally, one enlisted in the US Army as a Private (pay grade E-1). attended Basic Infantry Training (BCT) at Fort Polk, Louisiana (nearest BCT site to Fort Wolters, Texas), perhaps got promoted to the knightly rank of Prvate E-2, then proceeded to Preflight and Primary Flight Training at Fort Wolters, Texas. Upon beginning the Warrant Officer Flight Training one was promoted to Specialist E-5 (Temporary) for the duration of Flight training.
One member of my Class was Irish.. and another was a Canadian.
Upon completion of flight training we were issued a Warrant by the Secretary of the Army and the Rank of Warrant Officer One (W-1). One year later....we were promoted to Chief Warrant Officer (CW-2).
We had to be Officers to be Pilots....so we got promoted to W-1 one day...and the next day we received our Wings and Orders designating us as Army Aviators.
The Warrant Officer concept was used as the Army was limited by Congress to a certain fixed number of Officers and to meet the manning requirements of Army Aviation for Pilots....there was no way to do that had we been Commissioned Officers.
Warrant Officers In the US Military are Officers....not Enlisted Troops and fall between the Senior NCO ranks and the lowest Commissioned Officer Rank.
Woe be it if a brand new 2nd Lieutenant tries to pull rank on a CW4 (or now CW-5).