What is a "backup" flight?

I just had a 30 minute call with a friend who is a professional ticketing agent. There is nothing officially called a "backup flight", but he got the idea and explained it to me.

What happens is, when the gate agent thinks that you will not be able to catch the flight, either by telling him in person or if the system detects that and shows some notification to him. The agent will have to find a solution, either by finding another flight or by cancelling the whole thing in case there is no way to catch the flight in your preferred times.

In your case, the agent found another flight and add it to your itinerary, nothing special so far. You had concerns about two flights in the same itinerary, I asked you in the comments for a copy of the itinerary just to show that there must some sort of a code there, as systems generally will delete duplicate confirmed sectors automatically, one of them must had some code, something like UN or UU depending on the system, it could be something else. These codes mean something like "unable to confirm".

So, most likely you didn't have two confirmed sectors, one of them was confirmed and the other was there as an FYI with a special code next to it.

United seems to have changed their policy around backup flight bookings. while this was normal when you had a higher status to have a second option United does not do this. According to the agent on the phone they got told a couple of days ago that they are not allowed to put in backup flights anymore - even not for the 1k customers with a higher fare ticket (V fare to Europe). Reservation can be changed, but in result the original flights have to be given up.

This change in the policy will hit in particular frequent flyers which are usually travelling on busy times. In particular for the last connections at a day that means in most cases that you even loose the chance to reroute through other cities. By the time the delayed flight is in on the ground the last seats on flights going in the right direction are taken by others and you're stuck at the airport where connecting.

I understand that United is not interested in holding a lot of seats for all their customers. But in particular the frequent flyers who are dependent on a good service and are hit frequently by United's need to reschedule. One policy change by United more which screws the frequent flyers in particular.