For me on time performance is key. I want them to deliver me to the gate at the 'arrival' time, or earlier, come hell or high water. I don't mind if that means that they 'pad' their schedules.
When things do go pear-shaped, such as runway/airport closures or capacity reductions I want better information. Having me go to the airport after some people at BA already know the flight will be seriously delayed or cancelled is counter-productive. The infrastructure can't handle the mobs of people this causes, the staff can't deal with it, and much much much time is wasted by everyone (in particular me). I now avoid Heathrow, and BA, because this happens much to often there.
I once sat on a BA aircraft for over 4 hours when drizzle changed to freezing rain and every departing aircraft needed to be deiced. They did not have enough equipment to do this. While I remain happy that we eventually departed (two days before Christmas, we would not have got there any other way if the flight was cancelled) there has got to be a better way. As an aircraft engineer, there's a project for you.
BA's customer service recovery also is very poor, but that is not an engineering problem. Or is it … ?