Gained may be the wrong discription - it’s more like acquired/stolen. He’s probable talking about the CAL 83’ strike and a number of scabs were hired( SCABBED ) and maintained that seniority after the striking pilots returned later on.

There was also a reversal of seniority between the 570/539 groups after the 85’ strike and that seniority list was upheld after a couple of appeals and laws suits by the “fleet quals” and some among the 539 failed.