My husband holds a German passport with a green card. In the late 90's, he flew from SEA to FRA on AA to visit his family for 2 weeks. On the return trip he presented his German passport at the counter in FRA and the agent noticed that his passport was expired (they didn't notice it was expired when he left SEA). He thought no problem, there is a passport office at FRA so he wasn't worried. At the FRA passport office they told him he need to go to the city that issued the passport to get it renewed. His passport was issued in SEA by the German consulate. He told them that AA wouldn't let him fly to SEA with an expired passport. They didn't care, they have their procedures and couldn't do anything for him. He went back to the AA counter and pleaded with the agent to let him on. After a lot of begging, she finally let him on the flight. I still laugh when I think about this.