Britain is banning direct passenger flights to and from the United Arab Emirates from Friday, shutting down the world’s busiest international airline route from Dubai to London.

Britain said it was adding the United Arab Emirates, Burundi and Rwanda to its coronavirus travel ban list because of worries over the spread of a more contagious and potentially vaccine-resistant COVID-19 variant first identified in South Africa.

“This means people who have been in or transited through these countries will be denied entry, except British, Irish and third country nationals with residence rights who must self-isolate for ten days at home,” U.K. Transport Minister Grant Shapps said on Twitter on Thursday.

Emirates Airways said on their websites they would suspend all U.K. passenger flights from 1300 GMT on Friday when the ban takes effect. Etihad Airways said they would only suspend flights to the U.K., with those from the U.K. remaining unaffected.

Dubai airport, in a statement, advised passengers booked on flights due to arrive in the U.K. after the ban comes into effect to not go to the airport and instead contact their airline.

The U.K. transport department advised British nationals currently in the United Arab Emirates to make use of indirect commercial airline routes if they wished to return to Britain.

Due to border closures caused by COVID-19, Dubai to London was the world’s busiest international route in January with 190,365 scheduled seats over the month, according to airline data provider OAG.

Emirates and Etihad normally carry large numbers of passengers connecting from Britain to destinations like Australia through their airport hubs, meaning the decision to cancel those flights will have far-reaching implications.

The Australian government said it will add more charter flights from Britain if needed as a result of the Emirates and Etihad cancellations.

Eran Ben-Avraham, an Australian stranded in Britain due to strict limits on the number of arrivals in Australia, said his options for getting home were continually shrinking.

“At the moment it is only giving us three options of flying Qatar, ANA or Singapore Airlines,” he told the Australian Broadcasting Corporation. “Every day it is making it more difficult to get home. The flights back are anywhere from like 4,000 pounds ($5,487).”