Check your TSA PreCheck approval letter or email
Log in to your Trusted Traveler Program account
Look on the back of your Global Entry, NEXUS, or SENTRI card
Check your airline frequent flyer or travel profile
Review past flight bookings where it may have been saved
Contact the Trusted Traveler Program help center
Call the airline or travel agency where you enrolled it
If you do not have one, apply for TSA PreCheck, Global Entry, NEXUS, or SENTRI