1. Upgrade to a higher travel class. 1.1 During an online check-in taking place no earlier than 30 hours before departure or at one of the kiosks at the airport, KLM can offer passengers the option of a paid upgrade from Economy Class or Premium Comfort Class to a higher travel class for part of their trip.

Upgrading with KLM in 2026 is considered relatively easy and user-friendly, as the airline has heavily digitized the process. The easiest way is via the KLM App during the 30-hour check-in window, where "Last-Minute Upgrades" to Premium Comfort or World Business Class are offered at a discounted cash or Flying Blue miles rate. You can also use "Flying Blue" miles to bid for an upgrade through their "Upgrade with Miles" portal. At the airport, self-service kiosks often show real-time availability for paid upgrades right up until 60 minutes before departure. KLM is unique in that it often offers "onboard upgrades" if seats are available after the doors close, though these are paid and cannot be purchased with miles once on the plane. For the best chance, travelers should check the app exactly when the check-in window opens.