New and existing bookings: American will waive change fees for all new travel booked by March 31, 2021, including basic economy and award tickets. Customers can change their origin and destination cities, but a difference in fare may apply. If the airline cancels the flight, customers can request a full refund to their original form of payment united airlines flight change policy..
No one will tell you for sure besides the official representative of the air company you're using. For example, I am a permanent client of Ryanair and get all the info via these contacts https://ryanair.pissedconsumer.com/customer-service.html , I just don't trust other sources.