Delta, United, American, and JetBlue have all updated their policies to allow flights booked up until June 30, 2020, to be rebooked without a change fee. Southwest doesn’t charge for changes but has extended the deadline for using travel credits into 2022.
Of course the devil is in the details, so check your airline if this may impact you as some are more generous than others. Also, here is the whole story if you are interested:
I believe that this should be a permanent approach to flight credits. It would allow people who booked a flight with the full intention of taking that flight to be able to reschedule if something happens (work, personal illness, etc) without being forced to, in some cases, pay more for the change fee than the original ticket.