Travelling Toronto to London via Newark because cheaper than any direct flight. CO to Newark then CO codeshare on Virgin to LHR. Arrived at Toronto in the evening to find our CO was cancelled, next one would have missed the connection. So they transferred us onto Air Canada nonstop, who were not only all loaded and ready to go but the only seats available were in Business.
We got to Heathrow 3 hours earlier than our schedule, to see the inbound Virgin was so late, also by about 3 hours, that the next CO from Toronto would have connected to it anyway.
Lovely quick comfortable flight and all at a bargain fare. Not much profit made by Continental on us.
I was also once on BA London to LAX which was cancelled at the last minute, the pax for New Zealand were rerouted via Singapore later that day. It's not often you get rerouted the opposite way round the world !