Your statement is correct until 2016. On January 1, 2016 United Express must have NO MORE than 450 total aircraft, 153 of them can be 76 seaters. If they want more than 153 76 seaters they must park enough 50 seaters to remain below the 450 cap and add a NB fleet to mainline.

By the end of 2015 Delta will be capped at 450 RJs as well.

So if you look at the numbers above, it states that United is around 70 airplanes away from the 255 threshold, 40 are going to SKW and 30 have not been awarded a home publicly. After this if they want to add more 76 seaters they have to add a NB mainline fleet and continue to park 50 seaters. So United has to park 130 airframes to get below the 450 cap and continue to park airplanes to accommodate the 76 seaters. United has to park 200 50 seaters over the next 2 1/2 years. So if SKW inc doesn't get the other 30 seaters you will see 40 airframes come in and a huge chuck of the 200 that have to be parked will come from SKW inc simply because they are the whom has most of the 50 seaters. I counted less than 50 combined 50 seat airframes at other carriers. Delta also has another 30 airframes without a home and AA will likely spread the love around even more. I think they are using Eagle to drive down pilot pay but they will still shrink us as they transfer people to AA and attrition to other places.