I've seen several TV intrerviews with people who say if your flight was cancelled and you need to rebook do it online via the airlines app. If you do that do you just initiate a new trip and purchase? How are you reimbursed?

No, herb do not do a new purchase. You would rather try to do a change to your current itinerary. If you are already at the airport, try dong it online while standing in line waiting for an agent. If you are able to get it done online then just drop out of line. Otherwise, approach the agent with one or more alternative itineraries you would like.

if you can't do it on the app while waiting in line, try calling the airline while still waiting. If you an get through, the agent on the other end is likely to be less harried than the agent dealing with hoardes of angry travelers face to face.

In my experience the airline may automatically put you on a different flight, one that their algorithms say is the best available option. It helps to know for yourself what your options are - so doing a new dummy search will give you info you can use. Last time this happened to me I was still at home, and taking the same flight but 2 days later was the best option given the limited flights with availability, or the bad connections same or next day. The airline (AA) had automatically rescheduled me onto a flight that left 2 hours later, but had 2 connections and 2 or 3x the total travel time. That would have gotten me there the same day, but was far from ideal.

I had a such problem a few years ago and the airline give me the next flight in this destination