re: TSA Pre Check...

This is critical, your membership needs to match how you book with the airline (PNR is "Passenger Name Record" which is your real ticket in "the system.")

I have no idea why, but United always appends my middle initial to my first name, and it's somehow never caused a problem (LemmyLives David Johnson turns into LemmyLivesD Johnson on my tickets.) Delta never did this. Southwest and Lufthansa don't do it.

Check your boarding passes for the dreaded SSSS marker, too. I've only gotten that flag leaving Japan or Istanbul, never (that I recall) domestically, I have no idea why. The way you purchase tickets may be clicking you up a risk notch, which triggers Pre Check removal on flight legs.

With certain (usually international) airlines, even not having a salutation on your PNR, but having "MR." on your pre-check profile will be enough for it to throw an inconsistency that triggers airport fun. Look at *all* the data elements between your accounts.