When it comes to air travel, the term "transfer passenger" refers to someone who is making a connecting flight. However, there are a few different ways to describe this type of traveler. One common synonym is "connecting passenger," which simply implies that the person is in the midst of switching from one flight to another. Another option is to use the term "transit passenger," which emphasizes that the individual is not coming to the destination city, but merely passing through on the way to another location. Finally, some airlines and airports describe these travelers as "through passengers," which also emphasizes the idea of journeying from one place to another with an ultimate destination in mind.