Originally Posted by
tilhas
I really enjoy using Passbook to save my tickets. This is the first time today when I checked into my flight to LAX that I didn't get that option.
I redo the entire checkin using my phone and it only lets me email it to myself or print it.
I email it, it provides me with the link and when I open it it says MUST BE PRINTED...
Why??
Looks like you are flying to the USA from a pre-clearance airport. In these instances US CBP will not accept electronic BP so you must have a physical paper for them to add their stamp or otherwise review and markup. Also all cellphones need to be stowed while in CBP and all bluetooth handsets removed from your ear.
ETA: Missed AC681 comment which beat me to the punch.