As of February 19, 2021 the CDC states,
“If you plan to travel internationally, you will need to get tested no more than 3 days before you travel by air into the United States (US) and show your negative result to the airline before you board your flight, or be prepared to show documentation of recovery (proof of a recent positive viral test and a letter from your healthcare provider or a public health official stating that you were cleared to travel).
Effective 12:01am EST (5:01am GMT) on January 26, 2021, The U.S. Has issued an order requiring proof of negative status for Covid 19 virus for all passengers traveling into the U.S.
On January 12, 2021, CDC announced that all passengers traveling into the U.S. From a foreign country must show proof of negative test results for covid 19 within 3 days before the flight departs.
It is unclear how delayed flights will affect this order.
Negative result documentation must be provided before boarding the plane. These rules apply to any passengers 2 years old or above. There are some exceptions such as military personnel or law enforcement in the capacity of carrying out protective services. See the complete order for more specific definition of who is exempt.
For more clarity from the CDC click here > Order.
The order remains in effect until the Covid 19 pandemic is no longer declared a public emergency or is rescinded or modified by the Director of the CDC or until December 31, 2021. (Which ever occurs first)