They will blame it on the weather. TXL was a mess today and SXF was shut down for a short time (heard it in the radio). Overfreezing snow&rain was causing issues everywhere in the city. Are we talking about the same BER?
It's not as bad as on Tuesday, when TXL was shut down for a while as well but still not "ok".
Unfortunately that is the loophole the airlines use, although the air traffic is pretty much up to normal already.
Both airports were "shut down" only for a couple of minutes totalling about 70 minutes over the whole day, this was not causing any cancellations only delays. TXL has two runways, the usually able to operate from one while cleaning the other. When the ice rain was setting in they needed less then an hour to prepare runways and to resume operations. All cancellations out of Berlin were due of the destination airports not accepting flights! DL could have operated the flight just fine, maybe a 30 min delay or so. The way to the airport is another story..