The USAF started doing away with the Sextant and Cel Nav in the KC-135 in the late 1990's - early 2000's with the PACER CRAG mod (CRAG=Compass, Radar And GPS). This also eliminated the Nav position, however the ANG and Reserve kept many older navs on to allow them to retire. Younger Navs had the opportunity to cross train, some going to flight school to become pilots. I'd say we haven't used the Sextant in about 5-6 years.