In the missile called a "SAM", it's what the "A" stands for
The Stinger-RMP 
is so-called because of its ability to load a new set of .... U.S. Army soldiers from 
the 11th Air Defense Artillery Brigade stand next to a FIM-92A Stinger portable 
missile... [DOC] [TLE] MIM-23 Hawk - Wikipedia [PAR] The Raytheon MIM-23 Hawk is a U.S. medium-range surface-to-air missile.