I work as an Airport Director and find that these passenger statistics can sometimes be confused when we are discussing hub airports with many connecting passengers.
An important distinction to keep in mind: this is a count of total passenger operations, that is both the number of passenger enplanements or (boardings) “folks getting on aircraft” combined with a count of passenger deplanements (deboardings) “folks getting off aircraft”.
At an airport like CLT, 76.7% were connecting passengers in FY21. Local origin and destination (O&D) passengers departing or returning home (arriving) accounted for 23.3 % in FY21.
For the latest year, CY23, most of the 53 million passenger operations are transfer/connecting passengers arriving and deboarding (counting as one passenger operation) then boarding a second aircraft to their final destination (counting as a second operation, this time as an enplanement).
For example, if someone flies from Roanoke to Charlotte then boards a second aircraft for London, this is one person passing through the CLT terminal facilities with the airport counting two passenger operations for that day (one deboarding and one boarding). Roanoke counts one boarding on the first flight. London-Heathrow counts one deboarding on the second flight. Four total across two flights. But CLT (the transfer hub) gets the benefit of counting two passengers operations for that day.
When that happens, one individual person “counts” as two passenger operations rather than one. This also means that at a hub airport like CLT significantly less than 146,000 individuals are passing through the terminal each day. For the reason that 76%+ of the traffic counted as two passenger operations rather than one.
On the other hand, the local O&D passenger, for example flying from CLT to Las Vegas on Spirit would only count as one passenger operation for the day.
If you look at FAA reports - they are usually by calendar year and airports are ranked by the annual count of enplanements only. Generally speaking, airports that aren’t connecting hubs (the vast majority of airports) often have approximately double the count of enplanements. Most all airports tend to tout or publish the larger, more impressive number of total passenger operations (inclusive of boardings and deboardings).
For the sake of simplicity, you will see marketing people say “ATL had 100 million passengers travel through” or CLT had “50 million passengers travel through”. That’s not exactly true as it’s an overly simplified statement.
It isn’t 274,000 individuals per day at Atlanta because of how the major hub activity affects the counts. The BTS data also shows this understanding to be true.
https://www.transtats.bts.gov/airports.asp?20=E&Nv42146=PYg&Nv42146_anzr=Pun4y166r,%20aP:%20Pun4y166r%20Q17tyn5%20V06r40n6v10ny&pn44vr4=SNPgf
Hope this makes sense.
https://www.faa.gov/sites/faa.gov/files/2023-09/cy22-commercial-service-enplanements.pdf
http://www.stlannex.com/blogs_2020/blog_airport_connections#:~:text=Charlotte%20Douglas%20International%20(CLT)%20has,percentage%20at%20a%20meager%203.0%25.
https://filecache.mediaroom.com/mr5mr_cltairport/179771/download/CLT%20FY%202021%20Annual%20Comprehensive%20Financial%20Report%20FINAL%201.28.22.pdf