Originally Posted by SkyBuck

Sometimes Orbitz will work for situations like this; the "narrow the search to my preferred airlines" option lets you specify up to 3 airlines (or an alliance).

In this case (using 4 Nov to 11 Nov as arbitrary dates, since the OP didn't specify) Orbitz is not showing mixed NW/TK options, but NW flights routed MSP-ORD-AMS-IST with KL metal for the last two segments are pricing at $772 all in. If this fare is available on your dates, it's not only cheaper, but avoids the hassle of changing airlines and worrying about baggage fees.