What phase occurs after a flight has been precleared?

After a flight has been precleared, the phase that follows is immediate entry into the U.S. without inspection. Preclearance is a process that takes place when customs and border protection operations are conducted at overseas airports, allowing passengers to clear U.S. customs and immigration before arriving in the United States. This effectively streamlines the entry process, meaning when the flight lands in the U.S., passengers can disembark and proceed without having to go through further inspections or customs checks.

This contrasts with the other options, which imply additional processes or delays that may occur if preclearance has not been completed. For instance, customs checks after landing would not be necessary for precleared flights, and boarding without security delays or delays due to additional inspections would not be relevant in this scenario as they do not follow the preclearance context. Hence, the ability for passengers to enter the U.S. immediately upon landing is a significant advantage of the preclearance system.