While I was at Dow Airplane Patch, I went from Airman Second Class to Airman First Class, but never received any more money each month. When I enlisted, the ranks were E-1 Airman Basic; E-2 Airman Third Class; E-3 Airman Second Class; E-4 Airman First Class. Between the time that I made E-3 and E-4 they changed the titles for the lower ranks. Then E-1 was still Airman Basic, but E-2 became Airman; E-3 became Airman First Class; and E-4 became Sergeant. The rationale was that there were no Third or Second Class Airmen. Also the E-4's were allowed membership at the NCO clubs and by calling them Sergeant, it made them the same as the rest of the NCO's.
My life has had a number of little ironies and this is one of them.