Hi, I'm from the UK and have previously only travelled direct from Glasgow to Newark (and vice-versa). In a few months I'm participating in a tour of America. I fly into Newark then the rest is on a bus. My final destination is San Francisco. On the way back to the UK I have to fly San Fran to Newark then Newark to Glasgow. I only have just over an hour to get on my connecting flight to Glasgow. What I'm wondering is how check in works? Do I only need to check my luggage in at San Francisco? or do I need to collect in at Newark and then book it in again?