I was at a conference recently and all set to fly home. On my way to the airport, TripCase pushed me an alert that my flight had been cancelled. I quickly clicked on the Alternate Flights icon (the calendar icon above the departure information for a flight) and noticed there was another flight out later in the evening and seats were still available. I immediately contacted the airline and rebooked on that flight. I learned from the agent that most passengers on my flight were being automatically rebooked on a flight the next day, but, thanks to TripCase, I was able to learn about the cancellation and act in time to get home that night.
I can imagine that there are many other uses for Alternate Flights information in TripCase, like if your meeting ends early and you want to head home sooner.