docbert

As things stand today, for a UA metal flight :
* You CAN waitlist NOW for the later flight. If any seats become available on the alternate flight they will be automatically reserved for you, and UA will call to confirm that you still want them and will confirm you on the later flight

* You can NOT standby for a later flight on the day of flight. Standby is for earlier flights only (for the fairly obvious reason that if you standby for a later flights, and don't make it on, then you can't fly on your original flight!)

* You can NOT use do a confirmed same-day-change to a later flight. Partially this is because the later flight is probably more than 3 hours after your original flight so you end up in the same situation as standby, but it's mainly because the rules specifically disallowed it.

* You CAN use the "flat tire" rule, which is where you turn up at the airport after your original flight, and United will do their best to put you on a later flight. However, you must arrive at the airport within 2 hours of your original flight departing, and most importantly, there's zero guarantee that you'll get a seat at all. If the later flights are full, you're out of luck and lose the value of your ticket!

The same day change part is a little different for Continental operated flights. What is still unknown is what will happen to SDC post March 3. It's possible that you'll be able to do a SDC within 24 hours, including to a later flights. And it's possible you won't be able it. We'll all know more in just over a month...