Cargo loading tables from WWII in Africa


Sometime last year we found about 20 sheets like the one attached. These show the cargo, mail and passenger loadings for two engine aircraft operated by PAA-Africa during July and August 1942 just before the Army ATC took PAA-Africa away from PAA. It is my experience that someone at PAA would gather up records like this and put them into his files when he saw that some change was about to happen.
  Attached is one of those sheets.   For each of the sheets the first  two columns show the three letter code for the airports traveled. I can guess some of them but maybe not all. There are some schedules (oh those evil schedules) that can give us some clues about this. Now notice that the later columns show the weight of express, passengers and their luggage, and the mail. These three have three classes, X, F and B. Not sure what those mean!! So my question is, do you have any ideas about what these classes of cargo, passengers and mail might be?? Thanks.
David Crotty