For passengers travelling to Amsterdam from high-risk areas antigen tests are required by the Dutch government, in addition to the already existing PCR test requirement. The necessary procedures have also been put into effect. For a number of customers, the imposed 4-hour limit for this antigen test also causes practical problems, because not all airports in the world have antigen testing facilities. KLM helps customers where possible.
In Bulgaria, passengers are advised to contact Genica, the authorized Bulgarian laboratory for registering to the test:
https://web.genica.bg/register
Working hours are from 3.00AM up to the time to cover all flights to Netherlands.