As requirements are constantly changing, it is the traveller's responsibility to comply with their home destination and their transit requirements. Some countries no longer require testing like Australia & Singapore - you can proceed directly to check in as long you as you comply with any other requirements of your destination country like proof of vaccination.
If travelling to or transiting to a country that still requires a negative covid certificate you must bring the certificate to the airport with you. The certificate must be issued by a Doctor and include at least the following information 1. the date and time of the test; 2. the name of the individual tested, as stated in the passport; 3. at least one other personal identifier such as date of birth or passport number; 4. the type of test conducted; 5. the brand and make of the test; 6. that the specimen for the test was collected, and the test was carried out, by or under the supervision of a Doctor; 7. the result of the test (such as ‘negative’ or ‘not detected’); 8. the signature of the Doctor providing the certificate, as well as their Authority to Practice Number.
Passengers departing internationally from PNG are reminded that they cannot be checked in without a certificate of vaccination valid for travel. Vaccination Certificates valid for international travel includes (amongst others) the PNG International Certificate of Covid Vaccination (ICCV), the WHO yellow card, the Australian Covid-19 Digital Vaccination Certificate, as well as compliant certificates issued by other countries.