In a statement, United Airlines, has reported that following the continuous restrictions that exist due to the closure of the borders. I have decided that: Tickets purchased with origin outside the United States dated until July 31, 2021 will not charge extra fees for changes. This exception does not include flights purchased since May 1 in Basic economy
Also remember that within the U.S. flights they have also eliminated the change fee in the economy standard and Premium classes for flights that are made within the United States and between the United States with Mexico and the Caribbean And there will also be no change charges for other international trips that originate in the U.S.
Remember that you can enter www.united.com and you will get all kinds of extra information.