Which factor influences when the PA for international forms should be made?

The duration of the flight is a crucial factor that influences when the public address (PA) for international forms should be made. Longer flights typically provide more opportunities for the crew to inform passengers regarding essential details, such as customs forms and necessary procedures upon landing. By timing the announcement appropriately based on flight duration, flight attendants can ensure that passengers receive information at a point when they can most easily comprehend and act on it without feeling rushed or distracted.

In contrast, the other options may impact other aspects of the flight experience but do not specifically dictate the timing of the PA announcements for international forms. For example, while flight location may inform the content of the announcement, it does not directly correlate with when it should be made. The number of passengers could influence the delivery of the message in terms of clarity and volume needs, but it does not affect the timing relative to the flight's overall length. Similarly, the type of aircraft may determine certain operational procedures, but it doesn’t typically impact when to announce international form details.