Checking-In: You may not like to run through airports, so I recommend that you check in at least 1.5 hours prior to the flight time for domestic flights and 2.5 hours prior for international flights. Better an hour early than one minute late. You should also be aware if your airport has any security problems or issues that might require you to be even earlier. Take a book, relax. Also be aware of your airline’s policy. Your reservations are subject to cancellation within so many minutes of a flight.