I had to cancel BA flights due to needing surgery after an accident and they were helpful. They put the tickets on hold which meant that I could re-book for any time in the next 9 or so months (maybe 12) without having to pay the change fee. All I needed to do was pay any fare difference. Indeed I was told I could have re-booked for any destination, which seems quite generous, but in my case I re-booked for each of my original sectors. It is times times like this, and BA's helpful general approach, that generate loyalty (from me at least).