Originally Posted by
lds89
Because based on what you suggested, it wasn't an international flight. She was boarding Charlotte to LA. When she tried to board the international leg they didn't let her on, per your comment. Unfortunately, it's up to the passenger to understand the document requirements for their final destination, and the airline doesn't often check until departure from the gateway city (in this case, LA)
This. There's no need to check 6 month validity on a domestic flight (CLT - LAX). In her case, she probably used it as identification rather than passport verification.