The CDC has provided updated information for both domestic and international travelers regarding COVID-19:
Domestic Travel During COVID-19
Information for People Traveling by Air and Land within the United States and U.S. Territories
International Travel to and from the United States
CDC Guidance on U.S Citizens, U.S. Nationals, U.S. Lawful Permanent Residents, and Immigrants: https://www.cdc.gov/coronavirus/2019-ncov/travelers/international-travel-during-covid19.html
Airline partners’ COVID-19 updates:
Each airline has implemented different procedures in response to COVID-19, such as plexiglass shields at ticketing counters, seating adjustments, and mask requirements for boarding aircraft. Check with your airline for more information. Airline contact information and COVID-19 updates can be found on the Airlines at MEM page.