You're only there for 5 days, the 6th air day being your exception. Whatever you're classified as (preload, unload, etc) is your main job. If you signed a bid sheet for Saturday air then you're on that until they put out the next list to sign on again. I may be mistaken on the last part. If you never signed a bid sheet to work Saturday air then you aren't contractually required to show up and run Air on Saturday.