[FailerZ]

first you should be getting syntax error for that

Код:

if(PlayerClass[playerid] = AIR_TROOPER)

Correct it to

Код:

if(PlayerClass[playerid] == AIR_TROOPER)

Second, When the player is selecting the class you should set the variable of PlayerClass for the player to AIR_TROOPER so double check it.
And also make sure if you have your class defines it doesn't have the same value