If you cancel today, 24hr, no charge. Afterwards it is €50. Fyi

but....

the last flight of a KL747

probably will be on the same date day/month they received the first 747-100 and perhaps that will be a return from New York. (The received the first one in the winter of ‘71). First commercial service was to New York.

then KLM can truly say they have flown the 747 for 50 years.