Visit KLM's official website.
You can choose "MY TRIP" from the menu on the homepage. Just click it.
You can enter the BOOKING CODE or sign into your FLYING BLUE account to access your flight reservations.
You must include the family name together with the booking code if you select that option.
Following that, you will have to log in.
After logging in, you will be taken to a new page called "MANAGE BOOKING," which contains a number of options.
To cancel your KLM ticket, you must select the 'CANCEL' option here.
On the screen will now appear a number of instructions.
Carefully read them to prevent future problems, then do the same to finish the KLM cancellation procedure.
Read also : Finnair Airlines cancellation | Emirates Airlines cancellation