I have a 6:00 a.m. flight from IAD to SFO (conntecting to KIX) in a week. What time should I get to IAD? I can't see getting to IAD at 4 a.m. (two hours for an international trip)--especially since I expect to have only carry-on luggage. TSA Precheck seems to open at 4:30, but I have no idea how busy they might be at that time of the day. Any help would be appreciated.