Hi, newbie questions regarding intercontinental flights here. Thanks for any help!

I'm scheduled to fly MSN-DTW-AMS-CPH on DL138 and DL 9612. Is there any chance to get onto an earlier flight the same day without that costing me an arm and a leg? Goal is to end up in CPH as early as possible.

For example: If I go to the airport early, I assume I could try to get onto DL1509. What about the connecting flights, do I need to hope at every connecting airport that they pull me onto an earlier flight, or can they arrange all of it in MSN/DTW? The last leg is operated by KLM, btw.

Also: Should I call the hotline, and if so at what time (same date, or up to 24 hours in advance), or is that pointless?