One more question related to this. On my ticket (CGK - IST - IAD), it seems to defer to the US Government's testing requirements:
Our passengers are required to submit a negative PCR (nucleic acid test) or antigen test result that sample was taken maximum 3 calendar days before the departure time of their flight.
Of note, the policy requires a PCR test
or antigen test. Antigen tests are MUCH faster and cheaper than PCR tests, so will TK allow me to board with just a negative Rapid Antigen Test?