We booked a flight with air Canada, and we were rejected boarding because the flight was overbooked, they refused to compensate us and told us we had to rebook a flight that departs from another city. They even made us pay for the price difference between two flights and the transportation to that city.
One of my friend got the boarding pass first, but then air Canada told us that the plane is full so we cannot board. The airline admitted first that the plane was overbooked and we got kicked out because we bought the cheap tickets. But then, they quickly changed their reasoning to "you guys are late", even though the one of us "late" passengers got the boarding pass just a second ago.
Also not quite sure why they had to repeat again and again that we could have boarded if we have bought the preferred seat for some extra $$. If they are willing to sell some tickets for cheap, they should serve those who bought them!
Worst airline experience ever, I deeply regret being a loyal customer and accumulate over 20,000 miles with them.