Do you have to write the flight number for air transportatio

Air cargo to Korea needs to apply for China South Korea FTA certificate of origin, the fourth column of the certificate of origin needs to show the voyage number, then it has to wait until the flight number comes out to make this certificate of origin, and then send it to the customer for customs clearance and pick up the goods. In this way, the documents always arrive later than the goods. Now I want to ask a question: do you have to write the flight number in the certificate of origin of China and South Korea for air export to Korea? If not, we can apply for the certificate of origin in advance, and the customs clearance information can be sent to the customer along with the goods.