It appears as if the search mode on this scanner is divided into search banks. After pressing the SRCH button, you'd hit a numeric key to activate the band or bands you want to search. Per page 47 of the online manual I included below, it appears as the air band would be search bank 5. Pages 45 to 47 explain it more in depth
You want page 51 of the manual. The item is called Programming Custom Search Ranges. It will allow you to set up ten search ranges where you select the starting and ending frequencies. You can then just call up whichever you want to run. This is different from the programmed service searches.