It is rather typical that the BBC article says "it was not believed to be terrorism related". Aside from the fact that they feel compelled to mention terrorism in every sentence relating to aviation, and also that the definition of such is really in the eye of the beholder, surely such a damaging and irresponsible action that has known consequences is indeed what we would define as terrorism - even if the target of such is in fact the company rather than the public?
Link:
BBC NEWS | England | London | BA staff arrested over jet damage
Without prejudging what is of course "suspected" rather than "proven and convicted", may I be the first to say, what utter, utter idiots.