Way back in the stone ages (pre 2003), we were paid 4 hours per calendar day or what we flew if over 4 hours per calendar day.

The then owner, Dr. Jacob Schorr who inherited the CBA from the founder, didn't like paying a pilot 8 hours for a red eye turn from ACY. In CBA 2003, he demanded that he be allowed to pay for a duty day vs a calendar day. The NC attempted to build a system that was equivalent to CBA1999 for multi duty period pairings, but which didn't pay twice for single duty period. Ever since, the CBA has allowed the company to pay "the greater of" flight time, trip rip, or min per duty period (including an additional duty period for any RON longer than 22 hours).

Over the years, the company has learned how to build pairings that minimize the amount of credit for a pairing. If you study each pairing, you'll see that the pairings pay the least of each parameter.

Some will argue that we get block or better, which is basically true FOR THE PAIRING. What they don't realize is that the the "gotcha" is in the way the pairing is constructed. If you fly 18.5 during a 18 scheduled four day, you do get the 18.5, BUT under the old way, you'd likely have credited 22. Only when compared to a true calendar day guarantee do you realize how much the average costs us.

There used to be a Spirit pilot who posted here who had a great technical explanation of just how the pairings have evolved to where they are now, maybe he will jump in.

I'll say this, if you like four day pairings with one three leg day, one one leg day, one 21 hour sit and another long day, you'll love trip averaging.