Years ago after sever training issues attributed to background HR began splitting the classes - Heavy/Light. That way they would be able to somewhat control who gets into what aircraft... must have worked out better because it has been the same ever since. Traditionally, (I don't know of any exceptions) the first class date of the week has been heavy and the second class date has been light. Monday/Tuesday; Tuesday/Wednesday; or whatever mix they choose due to holidays, training day scheduling lineup, or whatever else may be in the cards... that has held true as far as I know -- first class heavy, second class light. If you are coming from a smiley faced carrier off the 74 you are probably bound for an early start. If you are an RJ guy with no international experience typically you are headed for a light class. In between? Flip a coin.

Best wishes and congrats on the calls.