Kl7421 744 Tncc-eham...
Is actually an positioning flight from DUS to AMS right now in FL100 inbound EHAM RW06.
Also the B777 was an position flight from DUS to AMS as KL7461.
KLM was doing one testflight with an B737 in the morning on the AMS-DUS-AMS routing which was positive without any affect to the aircraft. So they are now starting to ferry there stranded aircrafts from DUS back to AMS:
Greetings