Тем временем KLM предлагает менять купленные билеты на ближайшее время без дополнительных fee (но разницу в цене билета, если таковая будет, все равно придется заплатить):
KLM would like to offer you a helping hand by temporarily introducing the option to change your ticket free of charge. You can change the period in which you choose to fly as well as the destination. This option is valid for bookings made by 31 March 2020 for flights departing by 31 May 2020.