 With the FAA reporting record numbers of flights, it begs the question, how early is too early? Or how late is too late to show up for check-in? Airlines generally recommend two hours for domestic departures and three for international flights. But travel experts tell the Wall Street Journal people with carry-on bags only can shave off about 30 minutes. Same if you download your boarding pass ahead of time. Subtract 20 minutes for TSA pre-check.