Wait - I thought Global Entry included TSA Precheck. As least that what the Homeland site says. How do we reconcile TSA and CBP differences?
There is no difference.
Global Entry includes TSA PreCheck privileges. So does NEXUS and SENTRI.
BUT NOBODY who has PreCheck privileges (via Global Entry, SENTRI, NEXUS, or through having gone through the TSA PreCheck process itsself) is guaranteed to get to use the PreCheck line for every trip or every segment of every trip. In addition, only certain airports and certain airlines participate in PreCheck and the PreCheck lines are only open certain hours.
For each flight, TSA decides (based on their own, nonpublic criteria) who gets to use the PreCheck line and if a person is selected the participating airline puts a PreCheck notation on their boarding pass. You cannot just show up at the PreCheck line with a non-PreCheck boarding pass and your Global Nexus card and get into the line. You have to have the PreCheck notation on the boarding pass.
To be elgiible to use the Precheck line for any given flight segment: If you have Global Entry, SENTRI or NEXUS you have to give your airline your KTN (known traveler number) in advance of your flight. Different airlines have different ways of navigating this -- some you enter it in your frequent flyer profile before you make your reservation, others you enter when you make the reservations, others do it by phone, others you do it in person at the counter when you are checking in. *check with your airline to find out how they handle the KTN and to make sure it is actually attached to your
specific reservation*. At some point the airline shares the KTN (and presumably other) info with TSA, who makes the determination for each flight which passengers get to use the TSA PreCheck line, which is then marked by the airline on the boarding pass (and encoded in the boarding pass bar code).
Note, Global Entry and SENTRI and NEXUS also have additional Customs-related privileges and possibly some others (e.g. ability to apply for equivalent program in certain other countries) depending on the program.
SW