Here's the deal: Yes, your metabolism affects your size, and the faster your personal motor runs, the more calories you'll burn. But the truth is, a slow metabolism isn't the real reason you're packing on pounds. You are the reason.
As a general rule, arrive at the airport no later than two hours before your domestic flight is scheduled to depart. This is somewhat later than the typical suggestion of three hours for an international flight.
The airlines have a cut-off time of 30 minutes prior to flight time in order to check in (we almost missd it once). To be safe, for domestic flights, we arrive at the airport between 1 hour to 1.5 hours prior flight time, which gives enough time to check in, and get through security lines. For an international flight, I would arrive 2 hours before flight time.