As an example, If you are sailing on a Sunday, you can be tested any time on Friday, so if you are arriving on Friday (and presumably leaving the Netherlands also on Friday), you could do the test before you board the plane. If you are leaving the Netherland before that, you are correct that a pre-flight test would not work. My best suggestion would be for you to purchase the eMed proctored tests from RCL and take those when you arrive. I believe there are instructions on the RCL website on how to have those shipped to your hotel, or if you have any contacts in the U.S. you can have the tests shipped to them and have them either hold them for your arrival or send them to you in the Netherlands (I would do this option well before your cruise, because it can take time for all of the shipping/mailing to get them to you.