I have some KLM miles that are set to expire in a couple months and I would like to use them to upgrade a trip from economy to business class. What is the process to do this? Do I buy the economy ticket online, and then at some point I will be able to access this trip reservation and request a miles upgrade? When I went through the ticket purchase process (which I did not yet complete), I was never prompted to apply miles to an upgrade. Do I need to call customer service to upgrade? Does KLM post a chart anywhere showing the cost in miles to upgrade various types of trips?