This is a nice combination of the two airlines. The shadows cast by the different elements however need to be adjusted. The elements which are closest to the map surface will have a closer and a defined edge shadow while the Northwest Airline will cast a shadow which is further, softer, and with a blurred edge in relation to the others. Only where the Northwest airline crosses over the Delta airline will the shadow be more pronounced.
Good tip. I've tried reworking the shadows a bit. I think it looks better. Thanks.