And replacing them with what, exactly? Even if they get the maximum number of E175s allowed by the scope clause, the E175s AND CRJ900s have less than half of the seats of the DC9 fleet. Given how vigorously NW defends their market share, I rather doubt they're going to give up so much capacity so readily. The DC9s will solder on until replaced by E190s, C-series Bombardier, or similar - hopefully at mainline!!!