The uncertainty of flight delays can be nerve-wracking. Will you make that 40 minute layover... or will you be stuck in Newark for half the day? An alchemy of time of day, current weather, and the airports involved determine your fate.

You can obsessively check, but can't really predict, weather. The other factors, however, are a little easier to figure out ahead of time. Sites like the well-regarded FlightStats.com offer historical on-time performance for most routes. Punch in your flight info, and you'll be rewarded with average delays and details on past performance.

Maybe, now, you can relax.

Maybe.