The fact is that US citizens can enter the US with an expired passport. We live overseas and my wife was to start a sabbatical at a US university at the end of September. On Labor Day she realized that her US passport had expired and went running the next day to the local US Consulate for a renewal. Her travel plans did not qualify for an emergency passport and she was told that all passports are prepared only in the States so that it would take at least a month to get a new passport (no expedited passport from overseas). To make a long story short, all the explaining and cajoling did no good, but when she started to cry (loudly) in the waiting area, the consul told her that, as as a US citizen, she only had to prove her citizenship to enter the US and an expired passport is proof of citizenship. She asked if LY was aware of this and would they let her board, so he copied the relavant pages for her to show them. She had to tell this story to every supervisor along the way, including passport control at JFK, but she was allowed in. A month later her new passport caught up with her.