The first response to “How do I become a fighter pilot?” in the US military is always the same:  get a bachelor’s degree.  Both the Air Force and Navy require their pilots to be commissioned officers; in order to be an officer, candidates must have college degrees (though it matters little which one they have).

By contrast, the Army has a program that can take applicants directly from “high school to flight school.”  Many Army helicopter pilots are Warrant Officers, which technically fall between enlisted personnel and commissioned officers.  According to the Army,

Warrant Officers are technical and tactical leaders who specialize, throughout an entire career, in a specific technical area.

Basically speaking, Warrant Officers are “hired” by the Army to do one specific job for their entire career.  It is unlikely that WOs will ever command a unit or “broaden” their career beyond their technical specialty.  A Warrant Officer will never be a service Chief of Staff (though former WOs, who subsequently become commissioned officers, could).  Warrant Officers, even of the highest rate, are technically still outranked by 2nd Lieutenants (though any Lieutenant who tries to pull rank on a crusty old Chief Warrant does so at his own peril).

Many of the physical and medical requirements for being a Warrant Officer are the same as becoming an officer, but Warrant Officers do not require college degrees.  In fact, not counting the intervening military training courses, one can literally go from “high school to flight school” by becoming a Warrant Officer.