You will now need a negative COVID-19 test before flying to the US from the UK

Hours after United and Delta announced new COVID-19 test requirements for passengers traveling to the United States from the United Kingdom, the U.S. government said it would expand the mandate to all arrivals from the U.K.

The order, which will go into effect on Monday, Dec. 28, 2020, will require all travelers from the U.K. to provide a negative PCR or antigen test taken no more than 72 hours before departure, according to a statement from the U.S. Centers for Disease Control and Prevention (CDC).

Passengers must provide written documentation of the laboratory test result to their airline before boarding (either hard or electronic copies are acceptable, though we recommend keeping a paper copy on you just in case), and airlines must deny boarding to anyone without a negative test result.

"This new order is consistent with the measures that have been taken so far to increase our ability to detect and contain COVID-19 proactively and aggressively," said the statement from the CDC.

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The new screening requirements follow a string of travel bans and flight cancellations designed to contain a troubling variant of the novel coronavirus, which is thought to be up to 70% more transmissible, the CDC said.

Earlier this week, British Airways agreed to require New York-bound travelers from London to have proof of a negative COVID-19 test, following a request from New York Governor Andrew Cuomo. Virgin Atlantic and Delta also imposed screening requirements for New York-bound flights, the Associated Press reported, followed by United on Thursday.

Gov. Cuomo also implored the U.S. government to take action by requiring a negative test for all travelers on flights arriving in the U.S. from the U.K. and to consider banning all travel from Europe.

“It’s high time the federal government takes swift action, because today that variant is getting on a plane and landing in [New York-JFK], and all it takes is one person,” Gov. Cuomo said in a statement.

Though the nationwide mandate doesn't go into effect until Dec. 28, some airlines are already requiring passengers to comply. Virgin Atlantic began requiring all passengers ages 6 and up to provide a negative pre-departure COVID-19 test on Dec. 24. According to The Washington Post, Delta's requirement is the same. United's testing policy, which goes into effect on Monday, applies to children 5 and older.

Air travel between the U.S. and the U.K. has already been drastically reduced, and with strict Tier 4 travel restrictions limiting travel to, from and within many parts of England (including London and the city's surrounding boroughs) dreams of a travel corridor linking New York City and London seem to have been dashed. In fact, despite a surge in the holiday season travel, the industry seems to be slipping back into a hibernation similar to what we saw in the dark, early days of the coronavirus pandemic.

And experts worry these new travel restrictions and testing requirements may be too late to curb the spread of the new strain, which was first identified in late September. If it hasn't already reached the U.S., the current screening measures may not be enough to contain it.