Transit Passengers

Before travel, transit passengers must check with their airline and their final destination for specific requirements.
Transit via Sri Lanka is permitted, if the connecting flight is within 10 hours of arrival.
Travelers should check with their airline on the transit times.
The maximum permitted transit time at BIA for any passenger transiting through BIA must be less than 12 hours.
Passengers must have a confirmed connection later from BIA to a destination, and passengers must ensure that they do not exit the airport in the transit country on their way to Sri Lanka.
If passengers arriving from the airport in another country are discharged for more than 72 hours, they must obtain a new COVID-19 PCR report from that country, and it should be done within 72 hours prior to their departure.

Please also go through the given links regarding transit for more information.