df - yes, Sunday's early LHR-LCA flight.
How often? I am a BA Capt, and I think they say the average pilot might get one engine failure in their career... I am sure there will be some who have had quite a few, and many none. However, twice a year we are in the simulator, and they fail every time!
There was also a YAT 737 back into LHR engine fail earlier this week... so for the airport maybe a bit more often?
Catering (or other) truck hit aircraft... fairly often!
For your sister... yes a drag. But even by BA's "Heathrow woes" she still got to LCA. It took the original 767 problem, a 2nd 767 then brought into service, then knackered in less dramatic circs. BA still got her to LCA ~7hrs late... meanwhile the rest of the operation "adapted" - for instance a Stockholm 767 became a 757, and I later took a T4 A321 to ARN rather than an A320 to pick up the leftovers of that. There's much criticism of BA here, but even I was reasonably impressed with how Sunday's "issues" were coped with