Let's not forget throughs.

Here is the real order:

1. Through passengers
   
2. Crew change (if needed)
   
3. Preboards which includes COS, UM's, wheelchair and other assisted, news people with large cameras (my favorite), LEO's (?) and crew that will be riding jump seat.
   
4. Business Select INO
   
5. A-list Preferred INO
   
6. A-list INO
   
7. (There is a subcategory within A-list that I call serendipitous early boarders (SEB) that are generally clueless and travel naive that by some act of fate checked in after an A-list passenger canceled opening up a place in line that the computer assigns to the SEB.)
   
8. EBCI INO
   
9. Boarding for families with small children occurs after the last A and before the first B. That particular point may be in the midst of either A-list (rarely) or EBCI (more often) but hopefully neither as there can be a lot a family boarders. The good thing about family boarders is that they usually take whole groups of seats including middles. Also, families are not required to board at this time and may board in their assigned order.
   
10. B boarding passes INO
    
11. C boarding passes INO
    
12. Standby (rare but occasionally)
    
13. Folks that volunteered on a overbooked flight and failed to leave the area so they get called back to the flight and fly anyway turning their A or B boarding pass into a C with no seat left except middle seats next to people that should be COS but were too cheap to buy the two seats.
14. Late connecting passengers. They may be dead last, but can jump in line if they get there early enough. They will occasionally hold the plane at the gate for these folks.

INO= in numerical order. Yeah, right. Good in theory, in practice works better the lower the number. BS, A+ and A do this a lot and self-police the line around them to some extent. Back in the line, not so much.

See. Simple numerical order.