This is what I was able to find on UA's website:

Customers currently en route:May make one change to their return trip. Rules and restrictions regarding standard change fees, advance purchase, day or time applications, blackouts, and minimum or maximum stay requirements have been waived.

Origin and destination cities must remain the same. Booking class restrictions may apply.

Revised travel must be completed within 7 days of original travel date.

Customers who have not begun travel (wholly unused tickets):
May make one change to their travel plans without change fees or advance purchase requirement for the *same* itinerary. Changes must be made within 7 days of waiver travel dates. Booking class restrictions may apply.

For a *new* itinerary, one change may be made anytime within ticket validity without change fees.

All rescheduled travel (same or new itinerary) may be subject to higher fares if it does not meet original rule and booking code restrictions.


...Seems to me that you could push off the flight for a while as long as the availabily exists for your fare bucket...but I'm no expert. They only list the "within 7 days of original travel date" for the customers currently en-route.

I would guess that if you show up hoping for a VDB, or a non-voluntary (DB?) that you would be stuck with whatever they can come up with to get you on your way.