KLM crews may be proactive with their pax but their Customer Relations Department isn't. Over a five week period in March/April, three out of five flights I had booked with them were cancelled, one each from NCL, HEL and MAN. The first two resulted in trips with other carriers. The latter was a an example of terrible customer service - KLM agents @ MAN refused to place me and other pax with other carriers, stating that they could get us to our respective (European) destinations within 24 hours! My class of ticket booked with KLM was the same on all three flights but, in the latter case, I was told it was no longer KLM policy to place pax with other carriers in the situation described. In the end, I had to take a last minute, full fare ticket to HEL on another carrier. Plenty of seats empty on this one.
I am currently involved in an exchange of letters with KLM Customer Relations.