Roger,

I did ask about this today and was informed that they tried to keep passengers informed as much as possible, but at times there was much uncertainty as to what flights would indeed be going and when. The basic problem seems to have been that due to snow in various parts of the continent and icy conditions early in the morning at LHR, BA (and prob others) had both aircraft and crew stuck in some locations unable to return to LHR or simply hours off schedule. As a result a few planes and crew were out of position and some flights then could not operate due to either a lack of aircraft or crew or both. The same thing happened again today. Today it was largely due to snow in Paris, which then led to cancellation of services across Europe.

Hope this helps.