China has discussed diverting international flights away from Shanghai to other cities, as the financial center’s growing omicron outbreak puts pressure on quarantine hotels and isolation facilities, according to people familiar with the matter.

The country’s aviation authority asked airlines to nominate alternative ports of arrival for Shanghai flights, the people said, asking not to be named as the discussions were confidential. Passenger routes from Hong Kong won’t be affected, they said. One of the people said flights from Macau and Taiwan would also be exempted.

Officials cited stretched capacity at the quarantine hotels all travelers into China are required to isolate in, and concerns that space may be needed if the outbreak in Shanghai worsens. China isolates all virus cases, including those in the community, as part of its Covid Zero policy. 

The diversion may last for as long as six weeks, and could come into force as soon as mid-March, though it is still under consideration, according to one of the people. One airline is looking to add flights to Chengdu and maintain a service to Shanghai, just with fewer flights planned. The move won’t affect cargo flights, another person said. 

The Civil Aviation Administration of China didn’t immediately respond to a request for comment. 

Flights into Shanghai from Hong Kong had already been capped at 50% of usual capacity as the route saw increased demand from people trying to flee the city’s explosive outbreak. Shanghai, home to China’s main stock exchange and many company headquarters, is experiencing its most significant flareup of the pandemic, with the country’s strict border curbs largely keeping Covid out until more transmissible variants like delta and omicron emerged. The city reported 75 new cases on Friday, and said it would close most schools to in-person learning. 

China’s mandatory quarantine policy and border curbs have severely reduced the number of international flights into the country, with some carriers not flying there at all since the pandemic. Some foreign airlines are still operating despite punitive policies that have seen bans meted out to airlines that bring in Covid cases. China blocked some flights from the US as a precaution, rankling carriers and Washington.

United Airlines Holdings Inc., American Airlines Group Inc., Finnair Oyj and Etihad Airways PJSC are among the foreign airlines still flying into Shanghai.

Hong Kong’s outbreak, which went from a few hundred cases to the highest death rate among major economies in a matter of weeks, has triggered an outflow of people, with many seeking to get into the mainland where authorities are still deploying a zero-tolerance approach to the virus and trying to find and eliminate cases.