parents are flying from MEL-SYD-LAX on UA840 and the connect to US to CLT-ATL. have about 1hr connection time from LAX to CLT. parents are permanent resident so hopefully line is short, is the transit time enough? they have to recheck the luggage after custom. is UA840 on T7 or T8? US1687 is at T8 if not mistaken, so should be fine hopefully. any comments?