A good friend of mine that is retired Air Force with over 30 years of service and is now over 90 years old, was retired at E-8. However, the highest rank he achieved was Warrant officer back when the Air force still had them. I’ve asked him before why he didn’t get the W-1 rank at retirement and he just said he didn’t know and at the time he retired in the late 60’s, he really didn’t care. Does anyone know if the fact that the Air force got rid of warrants has anything to do with it? If he got it changed, would he be entitled to back pay if it’s more?

Most likely because E8's make more money than W1s. However, he can wear and call himself by the highest.

Current pay charts with over 26 years.

E8 = $5060.00
W1 = $4484.00