Why you shouldn't fly in the late afternoon or early evening

Don't take a flight that leaves between 3 p.m. and 9 p.m. Or if you do, you might want to prepare for a delay. 

I was looking at the U.S. Department of Transportation's on-time statistics for September, and the data is jarring. Fly first thing in the morning, and you're nearly guaranteed to be on time. Your aircraft likely spent the night at the airport, and so it's ready for the first departure. But by later in the day? The picture is not so rosy.

Let's use at Atlanta as an example. Flight that departed between 6 a.m. and 7 a.m. in September were on-time 93.3% of the time. But flights departing between 4 and 5 p.m. were on-time only 69.9% of the time. 

There are bunch of reasons for this, but the most common one is pretty simple. Short delays creep through the system during the course of the day, and eventually they start to add up. These delays might have been worse in September -- it was thunderstorm season in parts of the country -- but the same patterns are generally seen each month. 

Let's take a look at the data.