I, for one had a big problem with that lousy system, because in virtually every case, if the senior captain had wanted the original trip pairing, all he (or she) had to do was bid it. That way, they would have been the senior captain on the trip, and a junior captain would have gotten the relief captain pairing. I disliked the idea that a guy could be First-Classing all over the world, just to join another crew in mid-pairing, and take over the PIC duties, for a leg or two, then disappear once again, to deadhead somewhere else, to again take over a flight pairing.
It happened to me in February, 2003, when FedEx started flying into Kuwait in support of Operation Iraqi Freedom. They were asking for volunteers to do that flying, and so I did. The trip went MEM - DOV- FRA-OKBK (Kuwait International), then on to DXB (Dubai Int'l), then back to CDG and finally back to MEM. When we showed for the FRA - OKBK - DXB leg, we met another captain in ops, who informed us that he was going to be the PIC. Besides really ruining the cockpit harmony we had established, this guy sat in the seat the entire time, and flew a lousy airplane. We had to go around at Kuwait, because he had gotten too close to a C-130 on final, then he demanded a right turnout, instead of the left turnout that tower had assigned, because he "knew" that Iraqi was "over there to the left somewhere". As well, he didn't allow the F/O to fly the second leg, as he took that one too. Then after clearing customs in Dubai, he immediately left the terminal, found our hotel van and told the driver to depart for the hotel. By the time the F/O and I got outside, the van was gone and we had to take a cab. Needless to say, that put a rather bad taste in my mouth for the remainder of the time I flew as a Captain.
JJ