United Air Lines and Star Alliance came through on both our journey to Arizona and our journey back. On both occasions we could well have been stranded for hours or even a day or two.
We booked our flights from Ottawa to Phoenix and return via the Air Canada booking site. On the 22nd of February we arrived at the Ottawa airport to learn that snow and icing problems at Chicago meant that many flights through there were delayed or cancelled. After waiting in a non-moving line for 30 minutes or so, we reached the front to be asked to go to the next counter so our flights could be rescheduled. There we learned we had been rescheduled to fly through Philadelphia, not Chicago, to get to Phoenix. We were the last passengers to be placed on the initial flight to Phillie. The flights went well and we arrived in Phoenix just a little later than the original flight plans, though the flights were considerably longer. Star Alliance had come through, and at no extra cost to us.
On our return journey we also had to be rescheduled. A bus accident on the I-10 between Tucson and Phoenix meant that we arrived at the Phoenix airport more than an hour later than we planned. It was too late for us to make it through security and get on the flight. A quick word with a supervisor of the line-up resulted in us being moved to another counter where we were quickly and efficiently rescheduled. Again, there was no extra cost. The bus crash was a major item of news on CNN, and all were aware of the delays resulting from it.
Again we were the last ones placed on the flight from Chicago to Ottawa. (We did go through Chicago this time.) On arriving in Chicago we were too stuffed up with our colds and coughs to take advantage of an offer to be bumped from the flight, stay in a hotel overnight, get free flights to anywhere in the US, and free breakfasts, and fly into Ottawa early the next day. Two others took advantage of that offer.
Overall, we were very impressed with how United and Star Alliance worked to get us to our destination on both sets of flights. The only criticism we have is that the seating was so cramped and without padding as to be excrutiatingly uncomfortable on some legs of the journeys.