Sorry in advance if there is a better place to post this question, but I could not find one.

Has anyone had problems in traveling with a US passport that was expiring a few months in the future? I am planning to travel to Italy, Switzerland, and UK in June and July, with a passport expiring at the beginning of October. I was told by UA that this would not be a problem for flying to ZHR , as long as the flight was scheduled to return while my passport was still valid. However, it's possible I may fly into the UK first, with various travel among the countries. Anyone have experience with this? I would rather not renew the passport earlier than necessary, unless there is a good reason.