You're running late for a flight, so you decide you'll park on-site; the rates are higher than off-airport lots, but you'll save time because you'll be closer to the terminal—right? If you're traveling during peak periods (holiday weekends, Monday mornings), that may not be the case, since on-site lots tend to fill up quickly. You may be relegated to the farthest-from-the-terminal on-site lot (with no shuttle bus in sight), but still wind up paying as much as you would for a spot that's right outside baggage claim. You'll most likely spend less at an off-airport lot—as much as $30 a day less, when we searched
—and benefit from perks such as valet service, which will often get you to the terminal faster than the shuttle bus from on-site parking.