The TSA throughput number includes everyone going through the screening machines at each airport security checkpoint. The majority of this traffic is passengers who depart from an airport with a domestic or international flight. The number includes airline crew members like pilots, attendants, and maintenance technicians. People who worked with airport retailers (e.g. bookstores, restaurants, etc.) are also included. Some airport employees may skip security checkpoints with their special working badges through different doors.
The T100 traffic statistics include monthly traffic by flight (T100 Market Data) or flight segment (T100 Segment Data) by both U.S. and foreign carriers. It counts the number of passengers on a flight or a segment, including both local traffic and connections.
The DB1b data is a 10% ticket sample of U.S. carriers with more than $20 million in annual revenue. Some companies, such as FlightBI, scale up the DB1b input to 100% market size. Such data are air passenger traffic at the true O&D level (O&D numbers).
In general, TSA numbers are smaller than T100 numbers at large hub airports because most connecting pax don’t go through security checkpoints while T100 counts all pax on board. TSA numbers are higher than T100 at small airports because T100 only includes passengers while TSA includes crew members and people who don’t fly at all (e.g. Airport Retailers). Additionally, if a flight is canceled or delayed, passengers on the flight may go through the security checkpoint multiple times.
TSA numbers are generally higher than O&D numbers because
TSA numbers include crew members and people who don’t fly while O&D numbers don’t;
Some connecting passengers may go through security checkpoints if they walk out of the connecting airport or change terminals.
O&D numbers don’t count those passengers at the connecting points. Occasionally, you may see TSA numbers are smaller than O&D numbers at some small remote airports (e.g. in Alaska). That’s because those passengers may have got clearance through other channels.