That's actually a weak scope contract, the reason is labor law, and the RLA doesn't prohibit codeshare. That's why you have RJ's painted in Delta paint, to strike a contract with management in the late 80's/early 90's over code share protections to protect the high paying jobs. That was one issue, however, many more RJ's were later sold to protect the pension fund, then later to lessen bankruptcy pay cuts. Now today the market is pushing flying back to mainline on its own, yet pilots are for some reason paying for it. That's a bad deal, horrible actually, the only explanation is the unions are horribly corrupt.