Merging Scripts?

[ATAG_Colander]

Think of each class as a separate source file.
You can add between the class {}'s any function you want, just as you would on a source code.

So, you can copy the OnTickGame function and paste it inside the other's file "
public class Mission : AMission" and it will work.

Your only worry should be:
a) not have 2 functions with the same name (i.e. 2 OnTickGame's)
b) call the functions that are not called by the game from your code (i.e. isAiControlledPlane )