United Airlines customers with flights originating in the United Kingdom will need to present proof of a negative COVID-19 test within 72 hours of their flights to Newark Liberty International Airport beginning on Monday, Dec. 28.

“As we continue to experience a second wave of COVID-19 cases, it’s critical that we take any and all precautions to mitigate the potential for further transmission,” New Jersey Gov. Phil Murphy said of the new measure. “While New Jersey continues to strongly discourage all non-essential travel at this time, if unavoidable, international travelers should adhere to CDC guidance for pre- and post-flight testing and the recommended self-quarantine period.”

Customers will be asked to show proof of a negative molecular COVID-19 test or an antigen test that is taken within 72 hours prior to departure from London Heathrow. Same-day, pre-flight rapid tests are also available for ticketed passengers at the Collinson Testing Center located in Terminal 2 at London Heathrow.

The new regulation applies to customers over the age of five whose travel originates from the United Kingdom. People who are connecting to United flights at London Heathrow from another country are exempt from the testing regulation.

United passengers from London Heathrow to Chicago, Washington Dulles, and San Francisco also will be required to present proof of a negative COVID-19 test taken no later than 72 hours prior to departure.

For the month of December, United is operating four daily flights from London Heathrow to its hubs in Chicago, Newark, Washington and San Francisco. In January, United will operate two daily flights from London Heathrow to its hubs in Newark and Chicago.

Passengers on all United flights are required to wear masks and must complete a “ready to fly” checklist acknowledging they have not been diagnosed with COVID-19 in the last 14 days and do not have COVID-related symptoms.

Many countries began shutting down travel to and from the United Kingdom over the past week after health officials identified a new strain of the coronavirus that is more transmissible. British Prime Minister Boris Johnson ordered residents of London and southeast England to enter lockdown last week becuase of the new coronavirus strain.