I have gone through the TSA precheck application process and was assigned my KTN. I add the number when making reservations online, but the KTN is not on my boarding pass. When I receive my 'time to check-in email', the number shows up on the email, but not on my boarding pass. Delta customer service told me the TSA randomly pulls the number off of passes, the TSA told me it was the airlines mistake. I don't know how to get this corrected.