Flights within the USA or departing the USA- SSSS is not common but it still happens -- especially to last-minute, one-way travellers without frequent flyer accounts, and not paying with a credit card.
- Paid TSA PreCheck membership, NEXUS, Sentri, and Global Entry essentially protect one from SSSS.
- There are exceedingly rare random exceptions for paid TSA PreCheck, NEXUS, Sentri, and Global Entry members
- Depending on the airport and TSA staff, the process can be intrusive and humiliating or swift and passage to the front of the queue.
- SSSS is designated by airline software under the direction of the TSA.
Flights to the USA operated by US carriers, including Canada to the USA
Flights operated entirely outside of the US but operated by US carriers- A certain percentage of passengers must get SSSS screening regardless of their designated risk status.
- At "Category X" airports, passengers are interviewed (usually twice), and airline or contract security personnel may assign SSSS status.
- Paid TSA PreCheck, NEXUS, Sentri, and Global Entry do not matter. These risk assessment tools should be used, but they are not.
- SSSS status may be printed on a boarding card, written on a list for security staff, or a certain percentage of passengers are pulled aside continuously as they board the flight. It is estimated to be about 10 percent of passengers, and thus 30 selectees for a three-cabin 777-200 or "1.8" passengers on a Beech 1900.
- The screening may be benign and fast or even more intrusive than the TSA.
Flights operated by non-US carriers to the USA
Some airlines have software that will designate selectees.
- Some airlines ignore the selectee status entirely.
- Some require "additional screening," which might amount to another glance at hand luggage; others can be much more elaborate.
- For Canada-US Transborder flights, the additional screening is conducted at the checkpoint by CATSA, not by the airline or its contractors.
- Some carriers (Air France) have their own procedures for stopping random or non-random passengers on the jetway for frisking and hand luggage inspection.
- British Airways has a random alarm in its boarding pass reader, but this typically just triggers a hand luggage inspection.